A Practical Handbook for Growers
source; http://www.ksuaquaculture.org/PDFs/aquaponics_handbook_2021_final_022421.pdf
AQUAPONICS
Production Manual
KENTUCKY STATE UNIVERSIT Y
JANELLE HAGER LEIGH ANNE BRIGHT JOSH DUSCI JAMES TIDWELL • • •
Janelle Hager
Research and Extension Associate Aquaponics
Kentucky State University
janelle.hager@kysu.edu
Leigh Anne Bright
Senior Research Associate and Assistant Graduate Coordinator
Kentucky State University
leighanne.bright@kysu.edu
Josh Dusci
Graduate Research Assistant
Kentucky State University
dusci.joshua@gmail.com
James Tidwell
Professor and Chair
KSU Distinguished Professor
Kentucky State University
james.tidwell@kysu.edu
ii
School of Aquaculture and Aquatic Sciences
College of Agriculture, Community, and the Sciences
Kentucky State University
400 East Main Street
Frankfort, Kentucky 40601
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disability. 2021 KYSU-000086
KENTUCKY STATE UNIVERSIT Y
AQUAPONICS
Production Manual
A Practical Handbook for Growers
LAND GRANT PROGRAM
Contents
Authors …………………………………………………………………………………………………………………..ii
About the Authors……………………………………………………………………………………………….vi
Figure Credits………………………………………………………………………………………………………vii
Table Credits ……………………………………………………………………………………………………….viii
Forward……………………………………………………………………………………………………………………1
The Big Picture………………………………………………………………………………….1
I. Overview………………………………………………………………………………………..2
A. Definition………………………………………………………………………………………………….2
B. Context …………………………………………………………………………………………………….2
C. Importance………………………………………………………………………………………………2
D. System Types ………………………………………………………………………………………….3
II. Structure and Design……………………………………………………………………3
A. Fish Culture……………………………………………………………………………………………. 4
B. Solids Filtration……………………………………………………………………………………… 4
1. Sedimentation……………………………………………………………………………… 4
2. Mechanical Separation…………………………………………………………………5
C. Biological Filtration………………………………………………………………………………..6
D. Plant Culture or Hydroponic Subsystem ……………………………………………6
1. Media-based Systems…………………………………………………………………..6
2. Deep Water Culture ……………………………………………………………………..8
3. Nutrient Film Technique………………………………………………………………9
E. Sump ………………………………………………………………………………………………………10
III. System Technology……………………………………………………………………. 11
A. Water Sources………………………………………………………………………………………..11
1. Rainwater ………………………………………………………………………………………11
2. Well water ……………………………………………………………………………………..11
3. Municipal Water……………………………………………………………………………11
4. Surface Water………………………………………………………………………………12
B. Disposal of Waste…………………………………………………………………………………12
1. Mineralization……………………………………………………………………………….12
2. Direct Application……………………………………………………………………….13
IV. Grow Out Management …………………………………………………………….14
A. Suitable Species of Fish for Culture ………………………………………………….14
B. Species Overviews ……………………………………………………………………………….15
1. Tilapia ……………………………………………………………………………………………15
2. Common carp or Koi…………………………………………………………………..16
3. Channel catfish…………………………………………………………………………….16
4. Largemouth bass ………………………………………………………………………..16
5. Rainbow trout………………………………………………………………………………16
6. Barramundi…………………………………………………………………………………..16
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C. Fingerling Production and Supply …………………………………………………….16
1. Supply……………………………………………………………………………………………16
2. Production ……………………………………………………………………………………17
D. Fish Stocking…………………………………………………………………………………………17
1. Sequential Rearing ……………………………………………………………………..17
2. Stock Splitting……………………………………………………………………………..17
3. Multiple Rearing Units ………………………………………………………………..17
E. Plants………………………………………………………………………………………………………18
1. Staggered Crops …………………………………………………………………………19
2. Batch Crops………………………………………………………………………………….19
3. Intercropping……………………………………………………………………………….19
V. Feed…………………………………………………………………………………………… 20
A. Formulated……………………………………………………………………………………………. 21
B. Supplemental ………………………………………………………………………………………. 22
C. Alternative Diets …………………………………………………………………………………. 22
VI. Water Quality Parameters ………………………………………………………..23
A. Dissolved Oxygen……………………………………………………………………………….. 23
B. Temperature………………………………………………………………………………………….24
C. pH …………………………………………………………………………………………………………..24
D. Total Ammonia-Nitrogen…………………………………………………………………… 25
E. Alkalinity ……………………………………………………………………………………………….26
F. Cycling the System ……………………………………………………………………………..26
G. Corrective Measures …………………………………………………………………………… 27
VII. Plant Nutrient Dynamics………………………………………………………….28
A. Providing and Measuring Plant Nutrients………………………………………..29
B. Common Nutrient Deficiencies …………………………………………………………30
1. Nitrogen……………………………………………………………………………………….30
2. Phosphorous ……………………………………………………………………………….30
3. Potassium…………………………………………………………………………………….30
4. Calcium ………………………………………………………………………………………… 31
5. Iron………………………………………………………………………………………………… 31
VIII. Integrated Pest Management …………………………………………………32
A. Physical Controls…………………………………………………………………………………. 32
B. Biological Controls……………………………………………………………………………… 32
C. Chemical Applications……………………………………………………………………….. 32
D. Common Pests……………………………………………………………………………………..34
1. Mites……………………………………………………………………………………………..34
2. Aphids ………………………………………………………………………………………….34
3. Caterpillars………………………………………………………………………………….. 35
4. White Flies…………………………………………………………………………………..36
5. Thrips……………………………………………………………………………………………36
E. Disease Problems and Management ……………………………………………….. 37
1. Fish Disease………………………………………………………………………………… 37
iv
v
F. Common Fish Diseases and Their Treatment …………………………………39
1. Parasites ………………………………………………………………………………………39
a. Ich……………………………………………………………………………………………..39
b. Whirling Disease…………………………………………………………………….39
2. Bacterial Infections…………………………………………………………………….39
a. Columnaris ………………………………………………………………………………39
b. Aeromonas…………………………………………………………………………….. 40
c. Enteric Septicemia of Catfish …………………………………………….. 40
3. Viral Infections…………………………………………………………………………… 40
a. Tilapia Lake Virus………………………………………………………………….. 40
C. Plant Disease and Prevention ………………………………………………………….. 40
1. Bacterial Canker ………………………………………………………………………….41
2. Grey Mold……………………………………………………………………………………..41
3. Powdery and Downy Mildew …………………………………………………….41
4. Pythium………………………………………………………………………………………..42
D. Steps to Prevent Plant Disease in Aquaponic Systems ………………..42
E. Food Safety and Sanitation……………………………………………………………….42
IX. Controlled Environment Growing…………………………………………… 45
A. Types of Greenhouses…………………………………………………………………………45
B. Greenhouse Covering Options ………………………………………………………….45
C. Heating and Cooling Options ……………………………………………………………46
1. Heating…………………………………………………………………………………………46
2. Cooling…………………………………………………………………………………………47
D. Indoor Production ……………………………………………………………………………….47
X. Marketing and Economics………………………………………………………… 49
A. Economics …………………………………………………………………………………………….49
B. Marketing………………………………………………………………………………………………49
XI. Certifications and Regulations ………………………………………………… 51
A. Organic Certification…………………………………………………………………………… 51
B. Certified Naturally Grown…………………………………………………………………… 51
C. Good Agriculture Practices………………………………………………………………… 51
D. Hazard Analysis and Critical Control Points……………………………………. 51
E. Standard Operation Procedures ……………………………………………………….. 51
F. Best Aquaculture Practices……………………………………………………………….. 52
G. Propagation Permits…………………………………………………………………………… 52
XII. References………………………………………………………………………………..53
A. Extension Publications and Talks………………………………………………………56
B. Recommended Videos ……………………………………………………………………….58
C. Resource Pages……………………………………………………………………………………59
vi
About the Authors
Janelle Hager has nine years of experience working in aquaponics and six years
of experience in AP research. She developed the first fully online aquaponics
curriculum for both undergraduate and graduate students at KSU (AQU
452/552). Her research focuses on finding practical solutions to improve
aquaponic practices for small or limited resources farmers. She is currently
working towards her PhD in Plant and Soil Science at the University of Kentucky
focusing on food safety in aquaponics.
Leigh Anne Bright received her BS in Biology from KSU in 1997 and her MS
in Aquaculture and Aquatic Sciences from KSU in 2002. Her primary focus
area has been Production and Practical Diets in warmwater species. She has
27 peer reviewed publications. She has worked extensively with aquaculture
diet manufacturing, making trial diets and test ingredients on-site at KSU. She
has travelled both in the US and internationally, working with researchers to
manufacture fish diets in on-site projects.
Joshua Dusci is a recent graduate of KSU holding a master’s degree in
Aquaculture/Aquatic Sciences. His research focused on evaluating freshwater
prawn, Macrobrachium rosenbergii, as a biological solids control within the
hydroponic troughs of raft aquaponic systems. Josh is currently developing his
passion for aquaponics at his consulting company, Reel Aquaponics LLC, located
in Tulsa, OK. He continues to pursue opportunities in the private sector, with his
primarily client being Symbiotic Aquaponic LLC.
Dr. Jim Tidwell is Professor and Chair of the School of Aquaculture and Aquatic
Sciences at KSU. He received his BS in Biology from the Univ. of Alabama
in Birmingham, his MS in biology from Samford Univ., and his PhD in
Aquaculture from Mississippi State Univ. He was named a KSU Distinguished
Professor in 2014. He has authored or co-authored over 130 articles in refereed
scientific journals as well as eleven book chapters and served as editor on three
books. He has served as President of both the US Aquaculture Society and the
World Aquaculture Society. In 2019 he received the Distinguished Lifetime
Achievement Award from the United States Aquaculture Society.
vii
Figure Credits
Figure Number Credit
1, 4, 8 Rackocy et al. 2006
2 Timmons and Ebeling 2013
3a Somerville et al. 2014
3b Gary Donaldson
3c Davidson and Summerfelt 2005
5a EcoFilms Australia
5b Aquaculture Systems Technology
6 Backyard Aquaponics
7a Fox et al. 2010
7b Michael Tezel
9, 13, 21b Charles Weibel
10, 17, 18a, 18d, 18e, 20, 28 Janelle Hager
11 FAO 2016
12 Charles Shultz
14 Ryan Chatterson
15 Jesse Trushenski
16 Crouse 2017
18b, 18c, 18f, 19a, 19b, 19c, 19d, 19e, 19f, 19h, 19i, 19j, 21a, 21c, 22a, 22c,
22d, 25
wikicommons
19g Bessin 2003
22b, 22e Steven Koike
23a, 23b, 23c Joshua Dusci
24 Worley 2015
26 Andrew Biggs
27 Jeremy Pickens
Table Number Credit
1, 2, 3, 4, 5, 8, 9 Janelle Hager
6, 10 Somerville et al. 2014
7 Masser et al. 1999
11 Amy Storey
Bessin, R. 2003. Beet armyworm in Kentucky. University of Kentucky Cooperative Extension Service,
Lexington, Kentucky, USA. ENTFACT-308: 2p.
Crouse, D. 2017. Soils and plant nutrients. North Carolina Extension Gardener Handbook. NC State
Extension, Raleigh, NC.–URL:https://content.ces.ncsu.edu/extension-gardener-handbook/1-soilsand-plant-nutrients#section_heading_7276 [accessed 2020-09-22].
Food and Agriculture Organization of the United Nations (2016). FAO/INFOODS Global Food
Composition Database for Fish and Shellfish Version 1.0-uFiSh1.0. Rome, Italy.
Worley, J. 2015. Hobby Greenhouses. University of Georgia Extension Bulletin 910.
viii
Table Credits
Forward
The Big Picture
The world population is an estimated 7.7 billion and is expected to reach 10 billion by 2050. To feed this
expanding global populace, food production must increase by 30-50%. This increase would require that
land used to raise crops expand by almost 1.5 billion acres; that is about ¾ the size of the continental
United States.
In 2020, agriculture utilized almost 50% of the world’s vegetated land. The ongoing increase in atmospheric
CO2 levels, leading to increased global warming, would be exacerbated by the large-scale conversion of
forested lands to crop land necessary for food production. In addition, current agriculture production
accounts for 90% of all water used by humankind. This growth and consumption of resources is not
sustainable. Alternative ways to increase food production are required; we simply cannot just do more of
what we are doing now.
The World Resources Institute (WRI) recently published a report titled “Creating a Sustainable Food
Future” (Searchinger et al. 2014). The authors propose five “courses” or ways to produce more food without
increasing environmental impacts. Aquaponics is a concept that addresses several of these initiatives.
One of the WRI courses is to increase food production without expanding agricultural land. To
accomplish this, they state that “increased efficiency of natural resource use is the single most
important step toward meeting both food production and environmental goals.” As opposed to most
recommendations, they propose increasing production intensity as a pathway to sustainability. Aquaponics
is one of the more efficient and intensive food producing systems available. It is efficient in terms of the
amount of food produced per unit area, unit of water, and unit of nutrients added to the system, especially
in tropical or sub-tropical climates where heating costs are minimized.
Another solution proposed in the report is to increase fish supply. There is an indication that fish
consumption is predicted to rise 58% by 2050 (Searchinger et al. 2014). However, the WRI study assumes
that production from capture fisheries will actually decrease 10% during the same period. To meet
consumption demand, aquaculture will need to at least double output. However, that would add to land
use issues through the construction of 50 million acres of new production ponds. The authors pose that
aquaculture must also become more land-efficient and that water recirculation technologies could help
intensify production, reduce land use, and provide better pollution control.
Aquaponic production is a promising model for resource reuse and efficiency; this along with other
regenerative agricultural techniques can have local impacts on many of these pressing problems and serve
as a model for future technologies and developments.
1
I. Overview
The aquaponic system design channels nutrient-rich water from the fish culture system through plant
beds in direct contact with the roots to effectively feed the plants. In turn, nitrogenous waste is removed
through uptake by the plants for growth. Thus, the water is effectively cleaned and ready for reuse in fish
culture.
Definition
Aquaponics (AP) is a self-supporting food production system that combines recirculating aquaculture
with plant culture in the absence of soil (hydroponics). High-volume fish production results in nutrientrich water that can be used to provide nutrients for plant cultivation.
Context
Development of aquaponic systems resulted from the need to reduce costs associated with high-nutrient
effluent discharged from recirculating aquaculture systems (RAS). Known for intensive aquaculture, RAS
can produce large quantities of fish in a small volume of water. Some water is discharged and replaced in
the system over time, as solid waste and toxic nitrogen by-products (ammonia (NH3-N), nitrite (NO2-N),
and nitrate (NO3-N)) build up. Concentrated discharge from intensive aquaculture is a barrier to positive
consumer perception of aquaculture. However, these accumulated nutrients can be similar in composition
and concentration to hydroponic nutrient solutions and often exist in the form preferred by plants
(Rackocy et al. 2006). Combining these two production technologies provides an efficient and sustainable
method of growing fish and produce.
Importance
Hydroponics and intensive RAS each have ecological and economical drawbacks when considered
individually. Hydroponic crops rely on chemical fertilizers that are expensive, hard to source, and in some
cases are derived from rapidly disappearing natural resources. In intensive fish production, concentrated
wastes are generated (i.e. effluent) that require expensive treatment methods, leading to poor consumer
perception regarding environmental impacts. The high initial investment may be prohibitive to potential
producers, as well. Aquaponics provides the opportunity to utilize aquaculture effluent while growing
plants with a sustainable, cost-effective, and non-chemical nutrient source.
The integration of fish culture and plant production can provide several opportunities for farmers or
producers, including sustainable agriculture, marketing versatility, and generation of multiple income
streams. Environmentally, plant growth and yield in aquaponics can meet, or in some cases surpass, output
values of either hydroponics or soil-based agriculture (Pantanella et al. 2011, Savidov et al. 2005). The
shared core concepts of efficient water and land use, the ability to intensify crop production year round,
and use in geographic areas not suitable for traditional agriculture has driven a recent increase in the
popularity of aquaponics (Somerville et al. 2014).
While production values have been shown to be similar to both hydroponics and RAS (Pantanella 2013,
Savidov et al. 2005), the integration of these systems can make it more difficult to manage. Many groups
interested in aquaponic production are deterred by the high start-up cost and lack of proven models for
success. Understanding that aquaponics is a complete ecosystem is essential to provide correct conditions
for fish, plants, and bacteria, which are the three major groups of organisms that drive AP systems.
2
System Types
There are two main types of AP systems, coupled and decoupled. The coupled approach is widely used and
is based on feeding the system known nutrient-input amounts/values. The support for plant growth and
bacterial consumption (in the biofilter) typically come from commercial fish food and must be factored
into system input requirements. These ratios are used to ensure that toxic waste products from fish effluent
do not build up (due to an insufficient biofilter), excess nitrates do not occur (from not enough plants),
and nitrate deficiencies do not develop (from an excess of plants). Recommended operating ratios for
aquaponic systems will be covered in the Structure and Design section.
Given the wide range of growing conditions among fish, plants, and bacteria, coupled systems do not
operate at the optimum values for either fish or plants. The ideal nutrient environment for fish would
usually be nutritionally inadequate for most plants, and an ideal nutrient level for plants would be toxic to
most fish. For this reason, decoupled systems are being explored, though their use is not widespread. In
a decoupled aquaponic system, the RAS and hydroponic components are joined but operate as separate
systems that can be controlled independently (Goddek et al. 2016, Pantanella 2013). Typically, water
that feeds the hydroponic system does not enter back into the fish culture tanks after being filtered by
the plants. Instead, water lost though transpiration and evaporation in the hydroponic unit is replaced
with water from the RAS, which in turn is replaced with new water (Kloas et al. 2015). This setup offers
greater control over the individual system and allows each to be operated at their optimal range. Disease
treatment and nutrient deficiencies (or toxicities) are more easily managed, as well. Decoupled systems
are not as well researched as coupled systems and require producers to have a higher level of expertise in
hydroponics, plant nutrient management, and aquaculture system design.
II. Structure and Design
The majority of aquaponic systems follow the same basic design or “order of operations” (Figure 1). The
main components of aquaponic systems are a fish culture tank, solids filtration, biological filtration,
hydroponic component, and sump. The solids and biological filtration can either be combined (ex. mediabased system) or separated into different units (ex. deep water culture).
FIGURE 1
Order of Operations for aquaponic systems
3
Fish Culture
Fish tanks for aquaponics
come in a wide range of
shapes, sizes, and materials,
with selection being
largely based on culture
species. The majority of
large systems use round
tanks that either have a
flat- or cone-bottom. Use of
tangential flow will prevent
dead zones when used in
round tanks (Figure 2). Cone-bottom tanks allow solids to concentrate at the bottom (in the cone) and be
easily flushed from the system. Flat-bottom tanks are more widely available, but solids removal requires
additional steps to ensure proper removal of organic material dispersed across the bottom of the tank.
Square tanks may also require additional cleaning as solids or debris can settle in corners (Somerville et al.
2014). Sizing for fish culture tanks follow RAS principles, with a 3:1 width to height ratio being ideal for
proper water movement and flow. Fish tanks are generally the highest point of the system and water flows
via gravity to the solids filtration component.
Commercial-grade tanks are commonly made from strong, UV-stable materials like high-density
polyethylene (HDPE) plastic or fiberglass. On a smaller scale or in areas with limited resources,
intermediate bulk containers (IBC) or lined cement troughs may be utilized. Food-grade and UV resistant
materials are necessary as many repurposed tanks may have held chemicals or hazardous materials,
making them unsuitable fish intended for consumption.
Solids Filtration
Effective solids filtration is a key component to a well-functioning system and potentially the most
important aspect as it influences the efficiency of all other processes. Solids are mostly produced from
uneaten feed, fish waste, and bacteria biofilms (classified as suspended solids) (Timmons and Ebeling
2013). If waste is not removed, it can settle on plant roots (preventing uptake of nutrients), collect in
areas of low water flow (resulting in poor water quality), cause the build-up of noxious gas, and clog pipes
(preventing sufficient water flow) (Somerville et al. 2014).
The solids filtration utilized depends on the quality and quantity of feed entering the system, with
all designs coming directly from RAS technology. The two main categories of solids filtration are
sedimentation and mechanical filtration (Lennard 2012).
Sedimentation: Sedimentation refers to solids settling from the water column via gravity, which occurs in
the clarifier. Clarifier, or (solids removal) designs include baffles, radial flow filters, and swirl separators
(Figure 3a, b, c). Radial flow separators are most commonly used and have been shown to be more
effective at removing settleable solids than a swirl filter in RAS (Davidson and Summerfelt 2005). Baffle
and swirl clarifiers are similar in solids removal efficiency (Danaher et al. 2013). Recommendations for
construction material follow that of fish tanks mentioned above.
FIGURE 2
Use of tangential or circular flow
4
Proper sizing of clarifiers and appropriate water flow rate
are essential for effective solids removal. If relying solely on
a clarifier to remove settleable solids, a 30-minute retention
time is required. This simply means that most solids that can
settle via gravity will do so within 30 minutes. A water flow
rate of 5 gallons per minute for small tanks and 25 gallons per
minute for large tanks should be used to calculate the size of
the filtration tank needed. Filtration that is under-sized (or a
flow rate that is too fast) will not be adequate to remove fish
solids, resulting in accumulation further down in the system.
Likewise, oversizing the component is not ideal as it increases
the upfront cost, requires a larger footprint in the facility, and
results in a greater amount of water use through inefficient
discharge.
Clarifiers will only remove the large solid particles in the
water, leaving solids that are too small to settle out of the
water (Summerfelt et al. 2001). These suspended solids
must be removed. A practice made popular by the
University of the Virgin Islands is directing water from the
clarifier through tanks filled with orchard netting (Figure
4). Netting material traps fine solids, allowing clean water to
be skimmed from the surface. Other options for removing
suspended solids are fine mesh bags, women’s stockings,
filter pads, and others. These items may quickly become
clogged if settleable solids are not effectively removed in the
clarifiers.
Mechanical Separation: Mechanical separation is the active
removal of solids via a screen or media (Lennard 2012).
These filters are extremely efficient, removing solids larger
than 50 microns, resulting in less time spent on cleaning
and maintenance due to their convenient automatic
backwash feature. Examples of these filters include drum
filter (Figure 5a) and a pressurized bead filter (Figure 5b).
FIGURES 3a, b, c
Clarifier designs for capturing settleable solids: a) baffles, b) radial flow filters, c) swirl separator
FIGURE 4
Fine solids filter
FIGURE 5a
Rotating drum filter
5
Mechanical filters have a high price tag, often making them
prohibitive for small-scale practitioners. In addition, they require
more advanced knowledge to operate and are difficult to obtain in
developing countries. This type of filtration would be appropriate
for a large, decoupled aquaponic system or those that focus the
majority of their operation on fish production.
Biological Filtration
Biological filtration refers to the breakdown of ammonia (NH3
and NH4+) into nitrite (NO2) and then further into nitrate (NO3)
by naturally occurring, nitrifying bacteria. These bacteria live on
the surface area of media contained in a tank— collectively called
the biofilter. The process of converting ammonia to nitrate will be
detailed in the section on water quality.
In RAS, the biofilter is designed to operate at low pressure. There is a dedicated tank filled with substrate
like Kaldnes media, granular media, plastic balls, or other inert materials that have a large specific surface
area or surface area of the media per unit volume. The higher the specific surface area, the more bacteria
can grow on the media, translating to a higher ammonia removal capacity. Typical biofilter designs
for RAS include trickle towers, submerged media, fluidized beds, sand filters, and static bed filter. In
aquaponics, the biofilter can either be a separate unit or part of the system. In deep water culture (DWC),
the plant trough walls, raft bottoms, and plant roots provide a significant surface area for nitrifying
bacteria to colonize. Unlike RAS, the AP system itself typically provides ample surface area for bacteria to
colonize, particularly for coupled systems that are appropriately sized. The nutrient film technique (NFT)
system (see section below) is an exception, as only a thin layer of water is applied to the plants. If the
biofilter is a separate unit, it should be located after the solids removal unit.
Plant Culture or
Hydroponic Subsystem
The hydroponic portion of
the system encompasses the
majority of the facility footprint.
Three primary designs are used:
media beds, deep water culture
(DWC), and NFT.
Media-based systems: The
design of media-based systems,
sometimes called flood-anddrain, is fairly straight forward.
A container filled with substrate
is periodically flooded with
water from the fish tank. Water
then drains back to the sump (or fish tank) drawing oxygen into the substrate for plant roots and nitrifying
bacteria. The media bed supports the plant as it grows and serves as a solids and biological filter (Figure 6).
Due to relatively few components and ease of construction and operation, these systems are popular for
FIGURE 5b
Bead filter
FIGURE 6
Flood and drain system
6
hobbyists and in developing regions. However, it is uncommon to find commercial production using only
media beds as they are less productive than other types discussed below. Rule of Thumb for media systems
are detailed in Table 1.
A variety of materials can be used
as substrate, including pea gravel,
lava rock, expanded clay pebbles,
or other inert media; practitioners
may be limited by what is locally
available. Water flow in the system
is controlled by either a timer or
siphon. Using the timer method,
water is pumped for a set amount
of time, allowing the bed to fill.
When the timer shuts off, water
drains until the timer engages the
pump again. The siphon method
is often implemented using an
automatic bell siphon (Figure 7a) or loop siphon (Figure 7b). In both siphon methods, the pump runs
continuously, controlling how fast the bed fills and drains. Fox et al. (2010) gives comprehensive, step-bystep instructions for building, operating, and troubleshooting an automatic bell siphon.
7
Table 1: Rules of thumb for media-based aquaponic systems.
Rules of Thumb for Media-Based Aquaponic Systems
Substrate Characteristics • Porous to increase oxygen and water retention
• Provide adequate drainage
• Easy to handle
• Light-weight
• Cost effective
System Design • Plant beds should be at least 12 inches (30 cm) deep
• Water should remain 2 inches below the surface of the media to prevent algae from
growing in the surface of the media
• Media displaces 60% of the volume of the plant bed. Fish tanks or sumps should be
sized so the pump does not run dry and tank does not overflow during the flood and
drain cycle.
• 1:1 ratio of fish tank volume to plant bed volume for simple design involving solely a
fish tank and plant bed.
• 2:1 or 3:1 ratio can be achieved by addition of the sump (Figure 5)
Carrying Capacity • Low fish stocking density
• Separate solids filtration needed for increase fish density
• Feeding rate is 25-40% less than values reported for deep water culture
Water Flow Management • Fish tank volume should be circulated through the plant bed every hour
• Water flow
Maintenance • Cleaning required at regular intervals to remove solids
• Red worms can be added to move solids trapped in beds
FIGURE 7a, 7b
Bell siphon (a) or loop siphon (b)
8
Constant-flow media systems offer an alternative
to the flood-and-drain method. Heavily aerated
water flows into the media bed. Instead of a floodand-drain cycle, the water level stays constant by
using a standpipe. This drastically reduces the
size of the sump needed for this type of growing
system.
Deep Water Culture: This growing method
involves suspending plants in a floating raft,
allowing the roots to hang down into the water
(Figure 8). Plant roots are in constant contact
with nutrient-rich water from the fish tank.
Effective solids filtration is a requirement in these
systems to prevent solids from entering the plant
bed and clogging plant roots. Aeration must also
be provided in the plant troughs to maintain
adequate oxygen levels for plant roots and
beneficial bacteria. Along with their large water
holding capacity that keeps water quality parameters more stable, the underside of the rafts and lining of
the troughs provide adequate space for nitrifying bacteria to colonize. The design itself also provides a
cushion against power outages, as roots stay submerged in water despite loss of water or air flow.
FIGURE 8
UVI deep water culture system
Table 2: Rules of thumb for DWC in aquaponics.
Rules of Thumb for Deep Water Culture in Aquaponics
Substrate Characteristics • Rafts are commonly made from HDPE plastic or polystyrene boards
• Beds should be insulated to prevent temperature fluctuations in the system
System Design • Beds should be a 12 inches (30 cm) deep
• Width of bed may vary but typically are 4 feet wide
• Efficient solids filtration is needed to prevent solids from accumulating in the plant
beds
• Aeration is needed in fish tanks and plant troughs
• Water flow rate of 5-10 gallons per minute
Carrying Capacity • High fish stocking density achieved with solids and biological filtration
• Fish stocking density not to exceed 60kg/m3 (0.5 lb/gallon)
• Fish consume 1-3% of the body weight in feed per day*
• Feed input for leafy greens is 40-60g of food/m2/day feeding 32% protein diet
• Feed input for fruiting crops is 60-100g of food/m2/day feeding 32% protein diet
• Leafy greens stocked at 20-25 plants/m2
• Fruiting crops stocked at 4 plants/m2
Water Flow Management • 1-4 hour water retention time in plant troughs
• Long, narrow beds help water move through the system
Maintenance • Fine solids may accumulate in the troughs and will need to be removed
• Clarifier drained daily
• Fine solids capture cleaned weekly
*Exception is in early life stages where fish can consume 5-10% of their body weight in food per day.
9
Deep water culture (DWC) is more productive (kg of produce/m2 growing space) than media-based
systems; however, it can be more difficult to manage on a smaller scale. These systems are well researched
by the hydroponics and aquaponics industry and are commonly implemented in commercial settings.
Leafy greens and herbs, such as basil, do well in this production system. Fruiting crops like tomatoes,
cucumbers, and peppers can be successful with appropriate nutrient densities and structural support. The
DWC technique may not be suitable for areas where access to supplies or equipment is limited. Rules of
thumb for DWC in aquaponics are listed in Table 2.
Nutrient Film Technique: Nutrient Film Technique (NFT) technology comes directly from the
hydroponics industry. In this method, plants are inserted into the top of shallow horizontal channels. A
small film of water is pumped through the channel, coming into contact with plant roots that utilize those
nutrients for growth (Figure 9). NFT systems, like DWC, require sufficient solids filtration to prevent
contamination of plant roots. In contrast to DWC, NFT systems need a separate biological filter, as the
channel alone does not provide enough surface area for sufficient growth of nitrifying bacteria.
These systems are more complex to design, build, and manage than media-based systems. If channels are
not sized correctly, plant roots can disrupt water flow by clogging the pipes. This design assumes a degree
of risk, as pump failure can result in large crop loss if water flow does not resume quickly. However, NFT
can be a great system for urban areas or rooftops as they are lightweight, use very little water, and can be
made from easily sourced materials. Rules of thumb for NFT in aquaponics are listed in Table 3.
FIGURE 9
NFT system
10
Sump
The sump is the lowest point of the system and where water collects to be distributed as needed
throughout the system. Water quality samples can be taken here and amendments can be made without
overwhelming the fish or hydroponic components. While not a requirement, the addition of a sump
prevents the water level from changing in either the fish tank or hydroponic component. In other cases
where safeguards are put in place, the fish tank or hydroponic component can be used as the sump.
Table 3: Rules of thumb for NFT in aquaponics
Rules of Thumb for Nutrient Film Technique in Aquaponics
Substrate Characteristics • Channels can be made from pre-fabricated plastic, rain gutter material, or PVC pipe
• White pipes should be used as they reflect sunlight keeping the inner channel cool
System Design • Square or rounds channels are suitable
• Channel diameter should be appropriate for the crop’s root size
• Leafy greens – 7.5 cm pipe diameter
• Fruiting crops – 11 cm pipe diameter
• Channels should not exceed 12 m to avoid nutrient deficiencies in plants at the end of
the pipe
• Slope of channel need to be 1 cm/m to ensure an adequate flow
• Efficient solids filtration required as solids can clog tubes
• Heavy aeration required
Carrying Capacity • High fish stocking density of 60kg/m3 (0.5 lb/gallon) can be achieved with appropriate
solids and biological filtration
• Plant need a minimum of 21 cm between
Water Flow Management • 1-4 hour water retention time in plant troughs
• Long, narrow beds help water move through the system
Maintenance • Channels needs to be cleaned between harvest
• Back up pumps and generators are needed as plants are very vulnerable during
outages
*Exception is in early life stages where fish can consume 5-10% of their body weight in food per day.
11
III. System Technology
Water Sources
Sourcing water is an important consideration, as it directly impacts system management and performance.
Typically, 1-3% of total system water is replaced per day depending on climate, time of year, and crops
being produced (Somerville et al. 2014). Water is lost in the system through evaporation, transpiration into
the plant, and through normal processes of splashing, cleaning, and harvesting.
Water with a salinity above 0.8 parts per thousand (ppt) are typically not suitable for aquaponic production
as the majority of cultured plants do not tolerate even a small degree of salt (Shannon and Grieve 1998).
Common aquaponic crops with a salinity tolerance include lettuce (0.83 – 2.8 ppt), kale (up to 7.4 ppt),
Swiss chard (1.5 – 3.5 ppt), and tomatoes (up to 5.8 ppt) (Maggio et al. 2007, Shannon and Grieve 1998,
Shannon et al. 2000). Even though some crops do show an ability to tolerate salt, growth is compromised
at some point during production..
The majority of aquaponic producers utilize rainwater, well water, municipal water or a combination for
their systems.
Rainwater: Rainwater typically has a neutral or slightly acidic pH, slight calcium and magnesium
hardness, and no salinity (Somerville et al. 2014). In large systems, rainwater is generally best utilized in
conjunction with other sources to reduce overhead cost and improve sustainability.
Rainwater run-off can easily be captured from roofs or gutters and stored for later use. Water collected
from roofs should be treated prior to use, as they may contain bacteria and pathogens from bird or
rodent droppings. Considerations include areas that may receive acid rain, laws that prohibit collection,
and roof material and age. Some research has suggested that new and aging roofs are not suitable for
collection (Clark et al. 2008), as materials such as shingles, cedar, and uncoated galvanized aluminum can
contaminate water with chemicals, heavy metals, and pollutants.
Well water: Well water is a viable option for some producers. Considerations include potential
contaminants and bedrock composition. Chemicals that are particularly harmful include heavy metals,
iron, and sulfur. Aquifers with bedrock composed of limestone have high water hardness and alkalinity
concentrations. Alkalinity (bases in the water like carbonates, bicarbonates, and hydroxides) prevents
swings in pH, which is naturally lowered in aquaponics from nitrification. Alternately, producers with
very low fish production may require water treatment to decrease hardness and/or alkalinity before use
(Somerville et al. 2014). Lack of fish and subsequent feed input can cause pH to remain too high, making
certain nutrients inaccessible to the plant. Pumping rate of the aquifer will also need to be determined if it
will be the only source of water for an aquaponic system. This is particularly important in systems that will
require large water additions or replacement.
Municipal water: Municipal water is ideal for use in aquaponic systems. Chlorine in tap water eliminates
bacteria, pathogens, and algae, making it a safe and reliable source of water. Chlorine and chloramines,
however, must be removed before use as it is toxic to fish and will kill off the nitrifying bacteria.
Chloramine is basically a very stable molecule of chlorine bound to ammonia. Unlike chlorine alone,
chloramines cannot evaporate out of the water. This provides rural households with a safe supply of
drinking water but makes its use tricky for aquaponic producers. Free chlorine in the water can be gassed
12
off in 48-72 hours with aeration. Chloramines require chemical dissipation (ex. sodium thiosulfate) or
charcoal filtration. Given the small volume of water exchange, chloramines typically do not negatively
impact an aquaponic system. Typically, you can replace around 10% of the system water volume without
treating or testing for chlorine/chloramines.
Surface water: Surface water includes ponds, lakes, rivers, and streams. Surface water can introduce
pathogens, algae, snails, and other organisms. In addition, many surface waters are contaminated with
pollutants or agricultural run-off that pose a food safety threat to the organisms in the system and to
consumers.
Disposal of Waste
Recovery and digestion of fish effluent is more important in aquaponics than waste disposal. A large
portion of feed is excreted as solid waste. Nutrients essential for plant growth are trapped within this
concentrated slurry and should be recovered to reduce production costs and limit the need for nutrient
supplementation. Recovery of these nutrients moves aquaponic production towards a zero-discharge
system. Nutrients can be recovered through aerobic or anaerobic digestion of solids. Direct application of
nutrients to crop land or composting sludge may be appropriate.
Mineralization: Approximately 20% of the N and 50% of the P from the feed is utilized by the fish for their
growth (Timmons et al. 2018). The remainder of the N and P (70% and 30%, respectively) is excreted as
a waste product by the gills and as particulate waste (10% and 20% for N and P, respectively). Particulate
waste also contains macro- and micronutrients not absorbed by the fish.
Recovery of these nutrients can improve
plant growth and limit the need for
supplemental nutrients.
Mineralization of fish effluent functions
similarly to the processes that occur in
soil. In AP, concentrated fish effluent is
discharged into an offline holding tank.
Microbes aerobically (or anaerobically)
degrade organic solid materials, releasing
soluble inorganic nutrients into the water,
which are then available for plants to use
(Delaide et al. 2018, Goddek et al. 2018).
Only in an inorganic form are nutrients
available to plants. Under aerobic
conditions, heavy aeration is applied
to concentrated solids (Figure 10).
After 8-10 days, aeration is turned off,
solids are allowed to settle, and clarified water is released into the system (Pattillo 2017). Under anaerobic
conditions, bacteria decompose organic matter in environments with little to no oxygen. Anaerobic
digestion produces methane gas (CH4) that can be utilized as biofuel (Dana 2010) and concentrated
digestant that can be applied to greenhouse crops (Pickens 2015) or used for seedling production (Danaher
et al. 2009, Pantanella et al. 2011). Anaerobic digestion of fish solids is more complex to manage than
aerobic digestion and may be cost prohibitive due to the large digester volume needed (Chen et al. 1997).
FIGURE 10
Mineralization
Limited information exists on microbial contribution or environmental processes that underlay effective
aerobic mineralization of fish effluent; however, studies suggest that nutrient recovery from fish solids can
be significant (Cerozi and Fitzsimmons 2017, Cerozi and Fitzsimmons 2016, Goddek et al. 2018, Rakocy
et al. 2016, Tyson et al. 2011, Yogev et al. 2016, Khiari et al. 2019, Graber and Junge 2009). Preliminary
results from on-site AP research systems at Kentucky State University (KSU) show that aerobic
mineralization of fish effluent for 14 days resulted in a 143% increase (7.61 to 18.5 mg/L) in phosphate
(PO4), a 47% increase in nitrate (NO3-N; 28.5 to 41.7 mg/L), and ≥ 20% increase in Ca (57.97 to 74.23
mg/L) and K (27.38 to 32.7 mg/L) compared to system water (unpublished). However, even if nutrients are
recovered from effluent and provided in the right form and quantity, interactions with other nutrients and
water chemistry can sometimes make them unavailable to plants (Bryson and Mills 2014).
Direct application: Waste can also be applied directly as a soil amendment, composted through traditional
heat-treatment methods, or via vermicompost (worm composting). Direct application should be used as
a low-grade fertilizer or if the slurry is less than one percent solids. Heat-based composting of dewatered
fish solids requires additional expertise and labor cost but can add an important additional income stream.
Vermicomposting uses similar methods to traditional composting but does not rely on heat to process
waste. Worms consume organic matter, fragment and aerate the solid material, and can potentially provide
a supplemental live feed for fish (Yeo and Binkowski 2010). Compost can include vegetable waste or other
compostable materials from production. It is not uncommon for mineralized effluent to be bottled and
sold directly to home gardeners or small greenhouse operations; however, some restrictions may apply
depending on your local regulations.
13
14
IV. Grow Out Management
Proper management of fish and plants is a critical element that should be detailed in a production plan.
Whether large or small scale, producers must implement strategies for best operation practices. This part
of the plan should include, at minimum, fish and plant stocking densities, dates for planting and harvest,
and their location or movement within the system (Bregnballe 2010). Additional components should
include identification of a steady supply of fish year-round, maximization of space and resources, and a
tailored or modified plan based on culture species and individual objectives.
Suitable Species of Fish for Culture
Unfortunately, not all fish species adapt well to tank culture, just as not all animal species adapt to being
farm animals. Since fish are cold blooded, almost everything about their growth and health is influenced
by temperature (see Tables 4 and 6 for details). The temperature of the culture water will partially dictate
what species can or should be raised in your system. Other important factors will be how densely you
intend to raise them and for what purpose or market. The rule of thumb for stocking density is 0.5 pound
of fish weight per 1 gallon of water in grow out RAS. The following are considerations about what to grow
for specific markets.
• What is selling in your current stores or restaurants?
• Can you address niche markets such as farmer’s markets or are there minority groups in your area that
have specific preferences?
• What seasonal markets do you want to address?
• What product forms will you be willing to address?
• What is your ambient temperature for your growing period? What energy implications does that have?
What is the cost?
For some producers, fish are not an important part of the overall economics of the system and are
primarily “nutrient generators” for the plants. For
others, selling food fish is an important profit center
for the aquaponics system. Aquaponic producers
may have the benefit of providing a one-stop-shop
for both fish and vegetables. If that is the case, the
aquaponics producer should plan ahead on what
their final fish product will be. Will the fish be sold
live, whole on ice, or processed? For product forms,
see Figure 11. Once you are selling processed fish,
there are many more issues to be considered in
terms of product form and processing regulations,
such as:
• Do you have access to a certified processing
facility?
• Do you have current HACCP regulations for the
species you intend to process?
• What does the packaging cost?
• How will processing and packaging affect your
budget?
FIGURE 11
Fish processing forms
Several fish species have been successfully cultured in aquaponic systems. Overall growth parameters of
these are given in Table 4. Important factors when deciding on the proper species also include availability
of quality brood-stock or fingerlings, growth rate to market size, and feed cost and supply. Freshwater
species are preferred, as most of the plant crops produced in aquaponics have very low tolerance of
salinity. Also, hybrid striped bass (Morone chrysops x M. saxatilis), which can be raised in aquaculture
recycle systems, are reported to do poorly in aquaponics due to intolerance of the high potassium levels
supplemented to support plant growth (Rackocy et al. 2006), though they have been grown successfully
(Diessner 2013).
15
Table 4: Summary of fish species suitable for aquaponics.
Species Temperature
(C)
Total
ammonia
nitrogen
(mg/L)
Nitrite
(mg/L)
Dissolved
oxygen
(mg/L)
Crude
protein in
feed (%)
Growth
rate
Year-round
supply of
fingerlings
(US)
Market
value
($US/lb
live)
Consumer
Acceptance
Vital Optimal
Nile tilapia
Oreochromis
niloticus
4-34 25-30 < 2 < 1 > 4 28-32 600g in
6–8
months
Yes $3.00 Good
Common carp
Cyprinus
carpio
14-36 27-30 < 1 < 1 > 4 30-38 600g in
9–11
months
Yes NA Poor
Channel
catfish
Ictalurus
punctatus
5-34 24-30 < 1 < 1 < 3 25-36 400g in
9–10
months
Yes $2.00 Good
Largemouth
bass
Micropterus
salmoides
5-34 24-30 < 1 < 2 > 4 45-48 600g in
14-16
months
Seasonal $4.00-
5.00
Moderate
Rainbow trout
Oncorhynchus
mykiss
10-18 14-16 < 0.5 < 0.3 > 6 42 1,000g
in
14-16
months
Seasonal $3.00 Good
Barramundi
Lates calcarifer
18-34 26-29 < 1 < 1 > 4 38-45 400g in
9–10
months
No $8.00-
9.00
Good
Species Overviews
Tilapia: Tilapia (usually Oreochromis niloticus or the Nile tilapia) are the most cultured fish in aquaponic
systems. They are tolerant of both crowding and relatively poor water quality conditions. They do best at
water temperatures of 25-30°C. At temperatures < 24°C, their growth slows substantially, and they become
susceptible to disease. They breed readily and abundantly. In fact, if using mixed sex fish, unintended
spawning in the system can be a problem particularly in DWC beds where tilapia will consume all
available plant roots. Monosex fish (all male) are available and preferred. Tilapia are widely accepted in the
marketplace. If available, ethnic markets, which accept live or whole fish, should be considered. The tilapia
is most efficient when grown to ¾-1 lb. in final weight. For processed products, such as fillets, tilapia must
be raised to large sizes since they have low fillet yields (33% of body weight) compared to other species.
Producers who choose to culture tilapia can be in competition with imported frozen product or with large
domestic recycle systems, which drives down market price.
16
Common carp or Koi: The common carp and the Koi are the same species (Cyprinus carpio). The Koi is
just a colorful genetic strain. Although widely consumed in other parts of the world, there is no food fish
market for carp in the U.S. Carp are very hardy, have a wide temperature tolerance, and tolerate crowding
and poor water quality. Fingerlings for stocking are usually readily available. They can be marketed as
ornamentals, fetching high prices per fish. For systems that primarily use the fish as a source of organic
nutrients, Koi can be a good choice because of their hardiness.
Channel catfish: The channel catfish (Ictalurus punctatus) is a major aquaculture production species in the
southern U.S. It is widely accepted in the marketplace but brings a relatively low sale price, resulting in low
profit potential. Ethnic consumers may pay higher prices for whole, quality catfish. Although a good pond
culture species, the channel catfish is not as hardy as some people assume. In tanks they can be aggressive,
and injury during feeding may occur from barbs located on the head of the fish. At water temperatures
between 20-28°C, catfish are susceptible to a bacterial disease known as ESC (Enteric Septicemia of
Catfish).
Largemouth bass: Largemouth bass (LMB, Micropterus salmoides) have become a relatively popular culture
species. They bring high selling prices, as they have markets as both food fish and recreational stocking.
Bass will not readily accept artificial feeds as small fingerlings so producers must buy fish that have been
feed trained. So far, LMB growth in tanks is much slower than for fish grown in ponds (Watts et al. 2016).
Lack of domestication and confinement to the high-density environment of tanks contributes to additional
time to harvest for tank-cultured LMB. LMB fingerlings are available most of the year from sportfish
suppliers but the price differential is large. For example, in April or May, the price for a 2-3 inch fingerling
is >$1.25 USD per fish, but in June they are $0.30-0.40 USD per fish. Two-inch feed-trained fingerlings are
generally available in early June from suppliers in Arkansas and Alabama and 6-8” fingerlings are available
in the late fall (usually November).
Rainbow trout: The rainbow trout has the longest history of culture of all the fish considered here. While
the others are warm water species, the trout is a cold-water species with optimal temperatures of 14-16°C.
Because they evolved in cold-water environments, they need high levels of dissolved oxygen and have
little tolerance for poor water quality. Trout fingerlings are available in certain areas of the U.S. (Idaho and
North Carolina) but are not always available in small numbers. If conditions are properly maintained,
trout grow rapidly and are well received by consumers. Trout require a high protein feed, with a minimum
of 45% for juveniles and adults. Trout production for small-scale producers is challenging due to the high
cost of feed and competition with commercial markets.
Barramundi: The barramundi is a native of Southeast Asia and into Australia. Like the tilapia, it has been
successfully raised in different production systems. It is often sold in restaurants and markets as Asian Sea
Bass. It grows rapidly and produces a product that is well received. However, at present, there is no source
of fingerlings in the U.S.
Fingerling Production and Supply
Fingerlings for fish culture can either be obtained from a supplier or produced in-house. Availability, price,
number of fingerlings needed, and level of expertise are the main factors that determine the method of
choice. Type of species cultured, season, and location can also heavily influence the methods.
Supply: The best option for small-scale producers is to buy from a supplier. Suppliers should maintain
detailed breeding records, use high-quality broodstock, and implement Best Aquaculture Practices (BAPs).
In the case of fish fingerlings, cheaper is not always better.
17
Knowing when fingerlings are available for purchase will help ensure quality fingerlings. Certain species
such as bass, bluegill, and yellow perch fingerlings are considered seasonal and are easiest to find during
the summer months after they have been feed-trained. Small fish that are available off-season will likely
be stunted and would not achieve optimal growth rates. Species such as tilapia and koi can be bought
consistently year-round.
Regardless of the supplier, anytime fish are purchased they should be handled properly, acclimated, and
added into a quarantine system for 1-2 weeks to help prevent any disease/parasitic outbreaks within the
main production system. If the fish are healthy at the end of the quarantine period, then they should be
size graded and distributed into the main system. Addition of salt to the water during transportation
and holding can prevent disease issues by reducing stress on the fish and result in a higher survival rate.
Information on salting for transport and holding can be found in SRAC Publication No. 390 (Wynne and
Wurts 2011).
Production: If producing fingerlings in-house, the producer will need to determine the amount of fish
needed to meet production demands. Typically, oversizing fingerling production is done to maintain
maximum production capacity. Fingerling production will need to be done in a separate system to limit
the spread of disease and to ensure optimal conditions for growth. The producer will also need additional
tanks for broodstock, which should be of known lineage, age, and proper size (Egna and Boyd 1997).
Spawning can be natural or artificial but is typically natural in a commercial setting (Egna and Boyd 1997).
The benefits of producing fingerlings in-house include cutting out the fingerling supplier, ensuring quality
fingerlings, getting a quick supply of fingerlings, and potentially earning additional revenue from fingerling
sales. Some downsides include the need for more space, need for quality broodstock, need for fingerling
production expertise, and a higher initial investment.
Fish Stocking
Fish culture should be well planned, as mismanagement of densities within the system can lead to issues
with nutrient build-up/deficiencies, solids accumulation, water quality concerns, and poor fish health.
Consider that aquaponic systems typically do not operate with a fish density exceeding 0.5 pounds/gallon.
Three of the most common fish production plans are sequential rearing, stock splitting, and multiple
rearing units.
Sequential Rearing: Sequential rearing involves one tank, containing multiple age-groups of fish (Rackocy
et al. 2006), where the market-sized population is selectively harvested, and fingerlings are restocked
in equal number. While this seems manageable, the continuous grading required can be stressful on
remaining stock, leading to increased risk of disease and death. In addition, stunted fish remain in the
system, consuming feed that will not yield any return for operation costs. Carnivorous fish are not well
suited for this management strategy, as younger fish are susceptible to predation.
Stock Splitting: Stock splitting requires accession of fingerlings at a high rate, followed by halving the
population when tank biomass capacity is reached (Rackocy et al. 2006). Benefits include the ability
to remove stunted fish and better control over inventory. However, moving the fish increases the risk
of disease and fish loss. Swim ways, a permanent or temporary channel connecting tanks, have been
successfully installed to limit stress on fish but accurate counts and weights of the fish are hard to ascertain.
Multiple Rearing Units: Operating multiple rearing units is the most popular method of fish stocking and
management. This method utilizes several tanks connected by a common filtration system (Rackocy et al.
2006). When maximum biomass in one tank is achieved, the entire population is moved to a larger tank,
typically connected via a hatch or swim way.
18
The University of the Virgin Islands (UVI) in St. Croix uses a variation on the multiple rearing unit system.
They operate four fish tanks of the same size, with same-age fish in each, stocked in time increments. Fish
grow from fingerling to market size in one tank, with no movement until harvest. In this scenario, there is
always a tank that is either ready for or nearing harvest. While tank volume is not utilized efficiently, fish
stress and labor costs are decreased, while knowledge of stock inventory is increased (Rackocy et al. 2006).
Plants
Stocking and harvesting strategies can also be implemented in the hydroponic portion of the system. The
three most common strategies are staggered cropping, batch cropping, and intercropping (Rackocy et al.
2006). Their implementation and success depend on geographic location (tropical or temperate regions),
crop variety (leafy vs. fruiting crops), and market demand.
Aquaponic producers typically grow leafy green crops, which have a lower value per unit value and
high yield. Lettuce, Swiss chard, kale, basil, and other herbs are typically ready for harvest between 3-5
weeks from transplanting (6-8 weeks from seed), resulting in a steady income stream. Fruiting plants like
tomatoes, cucumbers, and peppers take 10-16 weeks to harvest, resulting in longer growing periods and
lower yields, but they have a higher individual value. Producers often grow a variety of crops to diversify
their markets and reach a number of consumer groups.
It is critical to invest time in a production strategy that realistically evaluates inputs and product output.
Market demands vary among countries, regions, and even among neighboring cities. Producers should
calculate the real-estate value of their system, often in price per square foot. To illustrate this, a comparison
between two types of lettuce can be used. Figure 12 shows two different types of lettuce grown at the
University of Virgin Islands in St. Croix. Although Parris Island romaine has a higher individual value ($/
head) than Boston bibb, when the planting density and growth period are considered, Boston bibb brings a
higher value per square meter of growing area per week than the Parris Island romaine. The main takeaway
here is that high density and frequent harvests may an increased value, even when individual value of the
crop is low. Information presented here is just an example and calculations should be tailored to a specific
crops, farm, market, and regional costs for production.
To understand if the crop is profitable, the cost of labor from seed to harvest, price of seed, propagation
supplies, and retail packaging will need to be subtracted from the price/m2/week. If the selling price
is below that of its “real-estate value,” the hydroponic portion may be operating at a loss. In addition,
producers may have multiple harvests from the same crop. Kale and Swiss chard are crops that can sustain
multiple harvests without a decrease in quality of the produce, therefore increasing the value of that real
estate. The strategies included here are not a comprehensive list but can be developed and adapted for
individual plants.
FIGURE 12
Value of crops
19
Staggered Crops: Staggered cropping is growing
multiple stages of crops in the same system and
typically allows a consistent and regular harvest to
be maintained (Somerville et al. 2014) (Figure 13).
For example, if a head of lettuce takes three weeks to
reach maturity, three stages are cultivated at the same
time, resulting in a weekly harvest. This method is
used with crops that are ready for harvest in a short
time, usually leafy greens or herbs. This method
maintains a constant nutrient uptake by the plants,
resulting in better control of the system and water
quality parameters, making system management and
outputs more predictable.
Batch Crops: Batch cropping is commonly used
when a longer growing period is required, such as
with tomatoes and cucumbers. Produce is collected
in batches as it ripens or becomes available.
Intercropping: Some producers will intercrop their
plants, meaning crops with a short time to harvest
are planted along with larger, fruiting ones (Figure
14). For example, if a producer is growing lettuce and
tomatoes together, the lettuce crop can be harvested
before the canopy of the tomatoes grows tall enough
to shade it out.
FIGURE 13
Staggered cropping
FIGURE 14
Intercropping
20
V. Feed
Fish feed is the driving force behind the aquaponic system. Fish feed is primarily made up of protein,
carbohydrate, and fat, with other ingredients like fiber, vitamins, minerals, and binders in smaller
quantities. The nutrient components of these ingredients, whether pre-digested by the fish or simply
broken down in the water, become the nutrient source for the plants in the system. However, for better
or worse, these are the only nutrients available for plant crop growth, so fish feed input requires careful
management. Table 5 outlines the feeding rate for fish based on body weight. To calculate the amount
of feed needed to support plant and fish growth, Feed Conversion Ratio (FCR) must be calculated. The
FCR is a ratio of fish diet fed in relation to fish flesh gained. The ideal FCR is 1, or 1 pound of diet fed to 1
pound of fish growth, but a more realistic number is closer to 1.4-1.8. FCR is calculated using the following
formula:
FCR = total feed input (g) ÷ total weight gain (g)
Protein is the limiting factor in fish growth but is also the most expensive dietary component. For these
reasons, it is important to choose the appropriate diet for fish. Inadequate protein will reduce growth
and too much protein is cost prohibitive and can lead to water quality issues. Figure 15 details protein
requirements for commonly cultured fish species.
Before feed is purchased for production, practical considerations include fish age, feed size, protein/
carbohydrate content, floating vs. sinking pellets, length of time in storage, and feed storage area. The rule
of thumb when choosing pellet size is that the pellet should be as big as the fish’s mouth. As fish grow, so
should the size of the pellet. Pellets are classified as float, slow sink, or sink, and the right choice depends
on the species being fed. Feed manufacturers are able to give directions on the right type of feed for each
production stage. Storing feed is actually a big consideration, as nutrient quality begins to decay after
production. Feed storage in a dark, chilled or frozen environment is preferable, as it delays nutrient quality
degradation but can introduce moisture resulting in moldy pellets. Molded feed must be thrown out, or
composted into a garden, but must never be fed to fish, as it may contain toxins produced by the mold.
Only enough feed should be purchased that can be fed in six months of straight production. When not
used, feed should be kept in a cold, dry place with low relative humidity.
Table 5: Recommended feed chart for tank culture of Tilapia.
Length (cm) Average Weight (g) Standard Feed Size Range of Feeding Rate
(% biomass/day)
Feeding Frequency
< 2.5 < 0.5 #00, #0, #1 Crumble 20 – 15 4x per day
2.5 – 6.4 0.5 – 5 #2 Crumble 15 – 10 4x per day
6.4 – 10.2 5 – 18 #3 Crumble 10 – 5 4x per day
10.2 – 15.2 18 – 75 1 mm 5 – 3 3x per day
15.2 – 20.3 75 – 150 1/8 inch (3 mm) 3 – 1.5 3x per day
20.3 – 33 150 – 450 3/16 inch (4 mm) 3 – 1.5 2x per day
33+ > 450 3/16 inch (4 mm) 1 1-2x per day
*Reproduced and adapted from DeLong et al. (2009) and Sawyer, J.D. (2019).
21
Formulated
Formulated feeds are nutritionally complete pellets that are formulated for specific fish and life stage
(Figure 15). Unlike other animal crops in agriculture, the nutritional needs of fish vary greatly among
species for protein, fat, and carbohydrate inclusions. A carnivorous fish who eats at the top of its food
chain, like a largemouth bass, requires a diet with high protein and low carbohydrates. On the other hand,
omnivorous or herbivorous fish, like catfish or tilapia, require less protein and can tolerate higher levels
of carbohydrate in their diets. This is important in aquaponics because the nutrient composition of the
feed pellet drives the nutrient load available to the plants. As the fish feed is consumed and excreted by the
fish, nutrients are released into the water as dissolved or solid particulates, which get circulated and used
for plant growth. For example, feeds with a higher protein content will deliver a higher amount of total
ammonia nitrogen (TAN) to the system, as nitrogen is primarily derived from the protein in the feed. The
amount of TAN produced from a particular feed per day can be calculated using the following formula
from Timmons and Ebeling (2013):
PTAN = Feed input (g) x Protein content (%) x *0.092 ÷ time
*0.92 represents = 0.16 x 0.80 x 0.80 x 0.90
– 16% (protein is 16% N)
– 80% N is assimilated
– 80% assimilated N is excreted
– 90% of N excreted as TAN + 10% as urea
Example calculation for 2,000 g feed per day at 32% protein:
PTAN = 2,000 g x 0.32 x 0.092 ÷ 1 day
PTAN = 58.9 g
This rate is equivalent to approximately 3% of the feed rate per day.
FIGURE 15
Protein requirement for commonly produced fish species
22
Commercial aquaculture feeds are extruded so that they maintain their integrity in the water (i.e. they
hold together and do not break apart easily when in contact with the water). Feed that is steam extruded
will float, where feed that is pressure/temperature extruded will sink. Feeds can also be slow sink, which
results from a combination of ingredient ratio (% inclusion of carbohydrate) and type of extrusion. The
type of feed required will depend on the biology and feeding nature of the culture fish.
Supplemental
A common question among small-scale and hobby aquaponic growers is if they can feed vegetable scraps,
insects, or loose grains to their fish. These are known as supplemental diets and only meet part of the
nutrient requirement of the fish. This is sometimes seen in traditional aquaculture practices in which fish
are contained in large bodies of water where they can scavenge additional foods from the environment.
Because aquaponics is a completely closed system, a complete diet must be fed. In addition, if fish must
expend energy to scavenge for loose food or scraps, they are not growing at their full potential. Providing
all their required nutrition in one, appropriately sized pellet allows the fish to convert more of that energy
into growth, rather than using it to find food.
Alternative Diets
Alternative diets are a great option to utilize bulk products that are a byproduct of another production
system, non-traditional ingredients, or even agriculture scraps. These diets would be prepared onsite and would still be combined in a ratio to meet both the nutrient requirements of the fish and the
plant crop. One area where this is seen is in the brewing of craft beer or spirits. The spent grains from
the fermentation process (brewer’s grains) typically have a protein content high enough to be used in
combination with another protein component, again dependent on the crops to be grown. Also utilized are
refuse from animal processing plants, scraps from crop harvest, or even earthworm or other insect sources.
One newer insect meal being used is black soldier fly larvae (BSFL). This is an especially good protein
source because the larvae can be “gut-loaded,” or fed whatever precursor food would most benefit the fish
consuming it, like foods high in Omega-3 fatty acids.
VI. Water Quality Parameters
Understanding water chemistry in aquaponics is essential to providing optimal growth conditions for
the fish, plants, and bacteria. By culturing fish in a recirculating system, all the essential elements for
survival— such as temperature, oxygen, pH, and water clarity— need to be provided. Like all organisms,
those cultured in aquaponic systems have optimum ranges for growth and survival. While there is overlap
between optimum water quality ranges for each organism, a compromise must be made in many aspects of
production (Table 6).
The five most important water chemistry parameters to consider for aquaponics are dissolved oxygen,
temperature, pH, total ammonia nitrogen, and alkalinity.
Dissolved Oxygen
Oxygen is required at high levels by fish, plants, and bacteria. Oxygen content is quantified by the
dissolved oxygen (DO) in water and is expressed as milligrams per liter (mg/L) (Somerville et al. 2014).
The intensive nature of aquaponic systems requires oxygen supplementation. Oxygen can enter the system
by agitation at the surface or by diffusers in the water column. Fish stocking density, number and type of
plants, amount of organic solids, biological oxygen demand, and temperature are all factors that determine
how much DO is needed (Rackocy et al. 2006, Wurts and Durborow 1992). DO and temperature have
an important relationship. Oxygen is more soluble in cold water than it is in warm water, meaning that
cold water can retain higher levels of dissolved oxygen than warm water. This is particularly important
for producers raising warm water fish or operating in areas that experience high year-round or seasonal
temperatures. It is recommended that dissolved oxygen be maintained between 5-8 mg/L. DO is difficult
to measure, as meters can be expensive or hard to find. In this case, producers can purchase DO aquarium
test kits or contact local Extension or universities for assistance.
23
Table 6: Recommended water quality parameters for aquaponics*.
Organism Temperature
(°C)
pH Ammonia
(mg/L)
Nitrite (mg/L) Nitrate (mg/L) DO
(mg/L)
Warm water fish 22 – 32 6 – 8.5 < 3 < 1 < 400 4 – 6
Cold water fish 10 – 18 6 – 8.5 < 1 < 0.1 < 400 6 – 8
Plants 16 – 30 5.5 – 7.5 < 30 < 1 < 250 > 3
Bacteria 14 – 34 6 – 8.5 < 3 < 1 – 4 – 8
Compromise for
Aquaponics 18 – 30 6 – 7 < 1 < 1 < 150 5 – 8
*Reproduced and adapted from FAO small-scale aquaponic food production (Somerville et al. 2014).
24
Temperature
Water temperature is more important in aquaponics than air temperature. Many water chemistry factors
are affected by temperature, such as the amount of toxic ammonia (un-ionized) present and the solubility
of oxygen. It also directly impacts the health and survival of both fish and plants. Fish are poikilothermic,
or cold-blooded. This means that their body temperature is dependent on water temperature. At
extreme temperature, fish will stop eating, becoming lethargic and susceptible to disease. In plants, high
temperature can reduce the uptake of essential plant nutrients, such as calcium, force early flowering in
cool weather crops, and increase potential for plant roots pathogens like Pythium spp. For this reason, it is
important to prevent wide swings in daily temperature. Shading or covering water surfaces, insulating fish
tanks and plant beds, and utilizing passive or solar heating in greenhouses are strategies many producers
employ. In temperate areas where temperature changes drastically from season to season, producers can
alternate fish and plant crops seasonally to reduce heating or cooling costs.
pH
The pH is a measure of the acidity or basicity of a solution. It is determined by the presence or absence of
free hydrogen ions (H+), where the more H+ present, the more acidic a solution is. An acidic solution has
a low pH. The pH is measured on a scale from 1-14, with 7 being neutral. A pH value below 7 indicates
a solution is acidic and above 7 indicates a solution is basic. The pH is recorded on a logarithmic scale
and thus is not intuitive for many practitioners. For example, if the pH of an aquaponic system measures
7, then after two weeks measures 5, the pH has not dropped by a degree of 2, but rather 100 times.
Understanding the pH scale is critical for water management and correction.
Fish, plants, and bacteria have specific tolerance ranges for pH. While they can tolerate parameters
outside their optimal range, sub-par conditions can greatly affect growth and survival. Fish can tolerate a
wide range of pH, from 6.0-8.5, but they need to be acclimated slowly to changes. The pH is particularly
important for plants and bacteria. All micro- and macro-nutrients are available to plants at a pH between
6.0-6.5 (Figure 16). Above or below this range, certain nutrients are not available to the plants. When pH
exceeds 7.5, plants quickly become deficient
in essential nutrients like iron, phosphorous,
and manganese (Somerville et al. 2014).
Conversely, low pH can have negative impacts
on nitrifying bacteria. Below 6.0, the ability to
convert ammonia to nitrate is greatly reduced.
There are many factors that influence pH.
Nitrification (discussed in the following
section) and fish stocking density drive pH
down by producing H+ and CO, respectively.
Amendments are needed to bring pH up to
suitable culture levels. Managing pH begins
with consistent monitoring and recording.
If pH is low, chemicals that increase total
alkalinity, like calcium hydroxide (hydrated
lime; Ca(OH)2), agricultural lime (calcium
carbonate (CaCO)), calcium potassium
hydroxide (KOH), or potassium carbonate
(K2CO), can be used. The addition of
FIGURE 16
Soil pH and nutrients
25
calcium and potassium bases are alternated to provide essential nutrients not contained in fish food.
Due to their high pH (10-11), these bases must be added with caution and in small doses, as to not raise
the pH too quickly. Nitrification constantly drives pH down by depleting the water’s total alkalinity and
release of H+ ions, so consistent monitoring is important. The need to lower pH is typically not an issue
for aquaponic producers, due to nitrification. Producers may need to amend their water source, however,
by adding hard water or chemicals to increase alkalinity, which stabilizes or increases pH. If the pH of the
system is constantly high, even after cycling, the first step is to make sure solids are not accumulating in
the system. Solids that accumulate form anaerobic (low or no oxygen) zones. When anaerobic conditions
develop, a process called denitrification, where nitrate is converted back into ammonia, occurs. Alkalinity
is released during this transformation, which stabilizes the pH.
Total Ammonia-Nitrogen
Nitrogen enters the aquaponic system as crude protein in the fish feed. Approximately 30% of protein in
the fish food is retained by the fish. Seventy percent is digested and released as solid waste or excreted
as ammonia via the gills or as urea (Timmons and Ebeling 2013). Total ammonia nitrogen (TAN) is
comprised of two forms that exist in a ratio of un-ionized ammonia (NH3, which is toxic to fish) to
ionized ammonia (NH4+ which in non-toxic). The presence of one form over the other is dependent on
pH and temperature. At high pH (basic) and temperature, there is a higher proportion of toxic ammonia.
At low pH (acidic) and temperature, ammonia binds to excess H+ ions and becomes the less toxic form,
ammonium. Generally, water quality tests will give the TAN value, which encompasses both NH and
NH4+. The exact value of toxic ammonia can be determined by taking the number that intersects the
recorded temperature and pH (Table 7) and multiplying it by the present TAN value (Masser et al. 1999).
Temperature (oC)
pH 6 8 10 12 14 16 18 20 22 24 26 28 30
7.0 .0013 .0016 .0018 .0022 .0025 .0029 .0034 .0039 .0046 .0062 .0060 .0069 .0080
7.2 .0021 .0025 .0029 .0034 .0040 .0046 .0054 .0062 .0072 .0083 .0096 .0110 .0126
7.4 .0034 .0040 .0046 .0054 .0063 .0073 .0085 .0098 .0114 .0131 .0150 .0173 .0198
7.6 .0053 .0063 .0073 .0086 .0100 .0116 .0134 .0155 .0179 .0206 .0236 .0271 .0310
7.8 .0084 .0099 .0116 .0135 .0157 .0182 .0211 .0244 .0281 .0322 .0370 .0423 .0482
8.0 .0133 .0156 .0182 .0212 .0247 .0286 .0330 .0381 .0438 .0502 .0574 .0654 .0743
8.2 .0210 .0245 .0286 .0332 .0385 .0445 .0514 .0590 .0676 .0772 .0880 .0998 .1129
8.4 .0328 .0383 .0445 .0517 .0597 .0688 .0790 .0904 .1031 .1171 .1326 .1495 .1678
8.6 .0510 .0593 .0688 .0795 .09114 .1048 .1197 .1361 .1541 .1737 .1950 .2178 .2422
8.8 .0785 .0909 .1048 .1204 .1376 .1566 .1773 .1998 .2241 .2500 .2774 .3062 .3362
9.0 .1190 .1368 .1565 .1782 .2018 .2273 .2546 .2836 .3140 .3456 .3783 .4116 .4453
9.2 .1763 .2008 .2273 .2558 .2861 .3180 .5312 .3855 .4204 .4557 .4909 .5258 .5599
9.4 .2533 .2847 .3180 .3526 .3884 .4249 .4618 .4985 .5348 .5702 .6045 .6373 .6685
9.6 .3496 .3868 .4249 .4633 .5016 .5394 .5762 .6117 .6456 .6777 .7078 .7358 .7617
9.8 .4600 .5000 .5394 .5778 .6147 .6499 .6831 .7140 .7428 .7692 .7933 .8153 .8351
10.0 .5745 .6131 .6498 .6844 .7166 .7463 .7735 .7983 .8207 .8408 .8588 .8749 .8892
10.2 .6815 .7152 .7463 .7746 .8003 .8234 .8441 .8625 .8788 .8933 .9060 .9173 .9271
Source: (Masser et al. 1999)
Table 7: Fraction of total ammonia in the toxic (un-ionized) form at different pH values and temperatures.
26
Through the process of nitrification, bacteria convert ammonia-nitrogen (NH3) to nitrite (NO2-
) and
then to nitrate (NO3-
). Ammonia and nitrite are 100 times more toxic to fish than nitrate (Somerville et
al. 2014). Plants primarily utilize nitrogen in the form of ammonium (NH4+), NO-
and amino acids such
as L-glycine (Rentsch et al. 2007, Sanchez and Doerge 1999). In a fully functioning aquaponic system,
ammonia and nitrite values should be close to zero and nitrate should be below 150mg/L. While fish can
tolerate much higher levels, upward to 400 mg/L (Timmons and Ebeling 2013), values exceeding 250 mg/L
can have negative impacts on plants (Rackocy et al. 2006). From a management perspective, it is important
to know the tolerance range of fish and plant species to optimize growth conditions. At excessive levels,
these toxic compounds can damage fish gills and stunt their growth.
Alkalinity
Alkalinity is an often-overlooked aspect of water quality but is essential in maintaining a stable system.
Alkalinity is a measure of water’s ability to buffer, or resist, changes in pH (Wurts and Durborow 1992).
The most common forms of alkalinity are carbonates (CO3-
) and bicarbonates (HCO3-
). These carbonates
bind to free H+ ions, a result of nitrification, preventing a drop in pH. Water with low alkalinity and a
steady rate of nitrification experience wide swings in pH, which can be detrimental to the health of fish,
plants, and bacteria. It is recommended to maintain alkalinity between 60-140 mg/L.
Alkalinity is often confused with water hardness. Hardness is determined by the quantity of positive ions,
namely calcium (Ca2+) and magnesium (Mg2+) ions, present in the source water. Water from limestone
bedrock has a high hardness (120-180 mg/L), while soft water has a low hardness (0-60 mg/L). Soft water
is associated with rainwater or groundwater from volcanic bedrock. Water lacking appropriate hardness
needs to receive amendments as Ca2+ and Mg2+ ions, which are essential for both plants and fish.
Alkalinity is not normally tested on a regular basis in aquaponics but is maintained through the addition
of bases to raise pH. In addition to those listed above, non-chemical measures to increase alkalinity and
pH include addition of finely crushed seashells, coarse limestone grit, and crushed chalk (Somerville et al.
2014). Placed in a mesh bag, they can be added to the sump until pH or alkalinity raises to the appropriate
level. The size of your system will dictate how long these amendments will be effective and how often they
will need to be replaced. Care must be taken to wash these items thoroughly to prevent contaminates from
entering the system.
Cycling the System
Cycling refers to the process of
establishing the biological filter.
This can take between six to eight
weeks (Figure 17). Nitrifying
bacteria are found naturally in the
environment, so the process begins
by adding a source of ammonia.
This can be accomplished through
adding fish, fish food, or water
from a well-established system,
or a combination of these. One
of the most common mistakes
when using fish to cycle a system is
adding too many fish initially. This
FIGURE 17
Cycling the system
27
causes ammonia levels to spike, often resulting in fish death. Starting with 20% of the total fish capacity
is a good rule of thumb. This allows the appropriate, system-specific biological organisms to colonize. If
using a fish-less cycling strategy, household ammonia can be used. It is important to source surfactant-free
ammonia, as it lacks detergents commonly added to these products that are unsuitable for the system.
Corrective Measures
• Low dissolved oxygen (below 5 mg/L): increase aeration, reduce feeding until corrected
• Low pH (below 6.0): add base (calcium hydroxide, calcium carbonate, potassium hydroxide or
potassium carbonate), reduce feeding until corrected
• High ammonia (above 1 mg/L TAN): reduce feeding until corrected, perform 20% water exchange,
check for accumulated solids, increase biological filtration
• High nitrite (above 0.5 mg/L): reduce feeding until corrected, perform 20% water exchange, increase
biological filtration
• Consistently high nitrate: reduce fish biomass or feeding rate, add more plant biomass
• Nitrate consistently at zero: increase fish feed or fish biomass
• Low alkalinity: add carbonate bases ex. (calcium carbonate, potassium carbonate)
*Note: Adding any base to the system must be done with care. Small additions of these chemicals result
in a large increase in pH. Base additions should be calculated before addition. Always err on the side of
caution.
28
VII. Plant Nutrient Dynamics
Most plants can be described by five main structures: roots, stem, leaves, flowers, and fruits. Dissolved
nutrients and water enter the plant via the roots through passive and active (requiring energy) transport.
The xylem, located in the stem, is a one-way transport channel that moves water and minerals from the
roots’ hairs into the main body of the plant through capillary action. The stem is typically the primary
support structure for leaves, buds, and other organs. The leaves are the powerhouse of the plant and
use solar energy to convert carbon dioxide (CO2) and water into glucose (energy) and oxygen (the
photosynthetic process). Glucose is transported to other parts of the plant via the phloem. Flowers and
fruits are the reproductive organs of the plant. Flowers require fertilization to develop into fruits. This can
be accomplished by wind, insects, birds, mammals, etc. In a greenhouse, flowers can be pollinated by fans’
gently shaking the plant, causing it to release pollen grains, or manually using a Q-tip or soft paintbrush.
Like in soil, plants grown in aquaponics derive their nutrients and energy for growth and reproduction
from photosynthesis, dissolved inorganic salts, and metabolites produced by bacteria and fungi. In
aquaponics, the nutrients are derived from feeding fish. Plants have some ability to select the rate at which
they absorb various ions. Just because the nutrient is provided in adequate quantities does not mean that
the plant is absorbing it. Plants have 16 essential nutrients required for optimal health and growth (Table
8). Essential nutrients are those that cannot be synthesized by the organism and are classified by structural,
macro-, and micro-, delineating how much is required by the plant. Nutrients can also be categorized by
their mobility. Mobile nutrients are elements that can be transported throughout the plant (usually to
new growth) as needed. Once immobile nutrients are deposited in the leaves (typically older or primary
leaves), they are fixed and unable to be transported to other parts of the plant. This can benefit producers
when signs of a nutrient deficiency are apparent by narrowing down the causative ions. Mobile nutrient
deficiencies occur in older leaves whereas immobile nutrients occur in new growth of the plant. Three
nutrients are not provided in adequate quantities in fish feed to support plant growth. These nutrients
are calcium (Ca), potassium (K), and iron (Fe). As discussed above, CaCO3 and K2CO3 are used to both
amend pH and provide essential nutrients. Iron is supplemented in the chelated form, which keeps it
soluble in the water and prevents it from oxidizing in the system. Fe-DTPA is recommended because it is
more stable at the pH suitable for aquaponics (6.0-7.5) and more cost effective than other forms.
Table 8: Sixteen essential nutrients required by plants for optimal health and growth. Circled elements represent
limiting nutrients in aquaponics. Mobile nutrients are represented by (m) and immobile nutrients by (i).
Essential Elements for Plant Growth
Structural Macro Micronutrients
Carbon (C) Nitrogen (N)M Iron (Fe)i
Hydrogen (H) Phosphorous (P)M Manganese (Mn) i
Oxygen (O) Potassium (K)M Boron (B)i
Calcium (Ca)i Molybdenum (Mo)M
Magnesium (Mg)M Copper (Cu)i
Sulfur (S)i Zinc (Zn)i
Chlorine (Cl)M
29
Providing and Measuring Plant Nutrients
Nutrients enter the aquaponic system in the fish feed. The amount of nitrogen that is available to the plant
is directly related to the protein content of the feed. The higher the protein content, the more nitrogen is
available for plant growth. Unfortunately, high protein feeds are very expensive, so feeding a higher protein
feed than your culture species requires is cost prohibitive. Nitrogen comes from the breakdown of proteins,
whose structural components are made up of nitrogen-rich amino acids. Approximately 20% of the
nitrogen and 50% of the phosphorous from the feed is utilized by the fish for growth. Much of the N and
P (70% and 30%, respectively) is excreted as a waste product by the gills, and the remainder (10% and 20%
for N and P, respectively) is excreted as particulate waste. Particulate waste, what we refer to in aquaponics
as “solid,” also contains macro- and micro-nutrients not absorbed by the fish. Utilizing this waste product
can be accomplished through mineralization.
Mineralization of fish effluent functions similarly
to processes in soil. In aquaponics, concentrated
fish effluent is discharged into an offline holding
tank. Microbes aerobically (or anaerobically)
degrade organic solid materials, releasing soluble
inorganic nutrients into the water, which are then
available for plants to use (Delaide et al. 2018,
Goddek et al. 2018). Nutrient-rich water can be
accessed via the settling of particulate matter and
siphoning water from the top.
Limited information exists on ideal environmental
conditions necessary to achieve effective aerobic
mineralization of fish effluent. Preliminary results
from on-site aquaponic research systems at KSU
show that mineralizing fish effluent for 14 days
resulted in a 143% increase in phosphate (PO4),
a 47% increase in nitrate (NO3-
N), and ≥ 20%
increase in calcium (Ca), magnesium (Mg), and
potassium (K) compared to system water (Table 9).
The particulate solids have an NPK ratio of 4:5:1,
as well as notable levels of Ca and Mg.
Plant nutrients are quantified through laboratory
testing of water and plant tissue. Testing can be
rather expensive for farmers (typically between
$20-$75 USD per sample) and results are not
immediate. Some universities may provide free
testing that can expedite the process and cut down
on costs. Measuring the electrical conductivity
(EC) of the water is helpful in determining the
concentration of nutrient salts but does not
quantify what nutrients are available to plants. The
acceptable EC range for aquaponics is between 0.5-
2.0 μS/cm.
Category Day 0 Day 14 % change
pH 6.54 6.48 -1%
EC 0.6 0.76 27%
MAJOR CATIONS (PPM)
Calcium(Ca) 57.97 74.23 28%
Magnesium(Mg) 13.31 17.54 32%
Potassium(K) 27.38 32.65 19%
Sodium(NA) 33.89 43.68 29%
Ammonium(NH4-N) 0.79 0 -79%
MAJOR ANIONS (PPM)
Nitrate(NO3-N) 28.47 41.74 47%
Chloride(CI) 46.76 62.61 34%
Fluoride(F) 0 0 0%
Sulfate(SO4) 53.29 58.92 11%
Phosphate(PO4) 7.61 18.5 143%
Carbonates(CO3) 0 0 0%
Bicarbonates(HCO3) 19.81 22.21 12%
Alkalinity(mg) 16.25 18.21 12%
TRACE (PPM)
Aluminum(AL) 0.01 0.05 400%
Iron(Fe) 1.95 1.95 0%
Manganese(Mn) 0.001 0.03 290%
zinc(Zn) 0.37 0.42 14%
Copper(Cu) 0.02 0.08 300%
Boron(B) 0.06 0.08 33%
Molybdenum(Mo) 0 0 0%
Table 9: Nutrient analysis of mineralized aquaponic
system effluent after 14 days.
30
Common Nutrient Deficiencies
A skill that is beneficial for aquaponics producers to
keep in their toolbox is the ability to visually diagnose
nutrient deficiencies. Once a plant exhibits symptom
of a deficiency, severe stress is already occurring. Early
detection and diagnosis are important.
Process of elimination can help growers successfully
identify a nutrient deficiency. Key factors include
recognizing where it occurs in the plant (mobile
or immobile nutrient); taking note of the general
appearance, such as color pattern or overall appearance;
and eliminating other factors that may be causing the
issue, such as light or heat damage. Below are common
nutrient deficiencies that occur in aquaponics.
Nitrogen: Although not very common in aquaponic
systems, nitrogen deficiencies most commonly occur
when the fish culture units are undersized for the
amount of plants in the system. Complete chlorosis
(yellowing) of older leaves is the first sign and can spread
to the whole plant if left untreated (Figure 18a). Other
signs are slow or stunted growth and plants that look
stretched. Nitrogen deficiency is typically not an issue in
appropriately designed, well-cycled aquaponics systems.
Phosphorous: Phosphorous deficiency in plants is
characterized by dark green and/or purple coloration
in older leaves (Figure 18b). It may also manifest at the
tips and edges of the leaves, giving them a burnt look.
Availability of P to plant is greatly reduced when pH is
outside the range of 6.0-7.5 and when temperatures are ≤
10oC (Islam et al. 2019). Symptoms are more noticeable
in young plants, which have a greater relative demand
for P than mature plants.
Potassium: Potassium deficiency does not immediately
result in visible symptoms. Leaf margins will appear
tanned, scorched, and/or have small black spots that
later aggregate into necrotic region (Figure 18c). Margins
of the leaves will cup downward, and growth will be
restricted. Potassium is a key nutrient for proper flower
and fruit development. Inadequate supply of K will result
in flowers’ dropping off the plant. High K concentrations
can reduce the uptake of Ca by the plant. K is a limiting
nutrient in aquaponics and must be supplemented to
maintain levels required for plant growth.
FIGURE 18a
Nitrogen deficiency
FIGURE 18b
Phosphorous deficiency
FIGURE 18c
Potassium deficiency
31
Calcium: Calcium is a limiting nutrient in aquaponics.
Deficiencies will appear on new plant growth, as it is a
mobile nutrient. Signs are small, deformed leaves that
may exhibit scorched margins (tip burn) (Figure 18d).
End blossom rot on tomato fruits is a characteristic sign
of a Ca deficiency (Figure 18e). Even when adequate
Ca is present, it is restricted from entering the plant in
humid conditions and has antagonistic relationships
with potassium (Somerville et al. 2014). In addition to
CaCO3, crushed coral can be used to maintain Ca levels
and increase alkalinity in aquaponic systems. Using
crushed coral is anecdotal but has been effective in
small and medium sized system. Using a source that is
sanitized is critical as to not introduce foreign organisms
or disease into the system
Iron: Iron is one of the more easily recognized
deficiencies. Fe deficiency is characterized by chlorosis
(yellowing) between the veins of the leaf (Figure 18f).
The veins themselves will remain green. As Fe is an
immobile nutrient, symptoms will appear on new leaves.
Signs appear similar to a Mg deficiency but are easily
differentiated, as Mg symptoms appear on older leaves
(Mg is a mobile nutrient). Chelated Fe is added to the
system to maintain Fe levels at 2 mg/L.
FIGURE 18d
Calcium deficiency in lettuce
FIGURE 18e
Calcium deficiency
FIGURE 18f
Iron deficiency
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VIII. Integrated Pest Management
Eliminating insect pests in aquaponic systems is more difficult than in traditional soil-based or
hydroponic growing methods. Common insecticides are typically toxic to aquatic vertebrates at very
low concentrations. Many practitioners implement an ecosystem-based approach to pest prevention and
reduction, known as integrated pest management (IPM). This strategy may implement a pronged approach
of physical, environmental, biological, and/or microbial controls.
Physical Controls
Preventing insects from entering the greenhouse is the best pest management strategy for aquaponics.
Prevention is accomplished through consistent monitoring and physical controls. The use of adhesive,
pheromone, or light traps can be used to monitor type of insect and level of infestation. Screens can
be an effective physical control and can be used on outdoor systems or to cover vents in a greenhouse.
Mesh size is an important consideration and should be as small as possible without restricting air flow
and ventilation. Screen size for common pests are 0.15 mm for thrips, 0.73mm for white flies and aphids,
and 0.8 mm for leaf miners. The most effective monitoring tool however, is the “farmer’s shadow” (close
monitoring by operators). Physical controls can also include a sanitation area for workers and production
of plant seedlings in-house.
Biological/Chemical Controls
IPM strategies can also incorporate biological and/or microbial controls. These controls have many
ecological advantages, including their host specificity, environmental beneficence, ability to be used in
conjunction with chemical application, and that they are nontoxic and nonpathogenic to wildlife, humans,
and other organisms not closely related to the target pest. Considering that these are precise, targeted
control measures, cost can often be substantial.
Biological controls utilize insect predators of the target pest to control population numbers. While
effective, use of beneficial insects may be cost prohibitive for smaller or hobby aquaponic systems. This
strategy requires a tight predatory-prey ratio, as prey can be quickly depleted, leaving the beneficial insects
with no food source. Predatory bugs such as spiders, ladybugs, praying mantis, bumblebees, and parasitic
wasps are effective in combating pests.
Certain plants such as lavender, basil, rosemary, marigold, chrysanthemum, petunias, and carnivorous
plants have natural oils and tactics that repel pests such as aphids, thrips, whiteflies, spider mites, and
caterpillars. A natural pest repellant can be achieved by having large quantities of these plants inside and
outside a plant production area.
Chemical Applications
Pesticides derived from biological or microbial sources are also effective and widely available. Biopesticides
are derived from natural materials such as animals, plants, bacterial, and certain minerals. Common
biopesticides include biofungicides (Trichoderma), bioherbicides (Phytopthora), and bioinsecticides
(Bacillus thuringiensis, B. sphaericus). B. thuringiensis (Bt) has become an increasingly common
mechanism to target specific vegetable pests. Bt consists of a spore that contains a toxic protein crystal.
Certain insects that consume the bacteria release toxic crystals into their gut, blocking the system, which
protects the pest’s stomach from its own digestive juices. The stomach is penetrated, causing insect death
by poisoning from stomach content and spores themselves. This same mechanism is what makes Bt
harmless to birds, fish and mammals, whose acidic gut conditions negate the bacteria’s effect.
33
Microbial pesticides come from naturally occurring or genetically altered bacteria, fungi, algae, viruses or
protozoans. These compounds can take different modes of action, including release of toxic compounds,
disruption of cellular function, and physical effect. Beauvaria bassiana, for example, is a fungus that gets
under the chitin (shell) of hard-bodied insects, resulting in dehydration and death.
Chemical pest controls used for aquaponic farms include neem oil and extracts, soaps, pyrethrum-based
products, and anything that is OMRI approved. These chemicals should be used in moderation and label
instructions should be followed to avoid any plant or fish damage. Before any chemical is applied to the
aquaponic system, the impact on the fish and biofilter must be considered. Limiting contact between the
chemical and water is critical and may be more difficult in deep-water culture and media-based systems.
The following is an example on how to calculate if a pesticide is safe to apply to the aquaponic system
(Storey 2016).
Note: Refer to the Safety Data Sheet (SDS) and find the LC50 value or the lethal concentration of a
pesticide at which 50% of the tested population dies. Rainbow trout or tilapia are often reported. The
lowest concentration over the shortest time should be used.
Example 1: Pyrethrum – the active ingredient in Pyganic 1.4
Step 1: Determine the LC50 value from the chemical’s SDS sheet – 0.0014 mg/L
Step 2: Determine the LC50 value for your system. Take the volume of your system in liters and
multiply it by the LC50 (96 hr) value. Let’s use a 2,000-gallon (7,580 L) system as an example.
7,580 L/sys. X 0.0014 mg/L = 10.61 mg/system
Step 3: Take the pyrethrin concentration and determine how much pyrethrin is being mixed.
The label recommends mixing 1–2 fluid ounces of Pyganic 1.4 with every gallon of water in
compressed sprayers, which is between 2–4 Tbsp/gallon. In a 2,000 gallon system, the entire crop
can be sprayed with 0.75 gallons of mix, which at the highest application rate is around 3 Tbsp (or
1.5 fluid ounces).
The label tells us that 0.05 lbs of active ingredient (pyrethrin) is the equivalent of 59 fluid ounces.
0.05 lbs pyrethrin/59 fluid ounces = 0.0008475 lbs pyrethrin/fluid ounce
0.0008475 lbs pyrethrin/fluid ounce X 453,592 mg/lb = 384 mg pyrethrin/fluid ounce
Step 4: Determine how much pyrethrin is being applied to the system.
1.5 fluid ounces/system X 384 mg pyrethrin/fluid ounce = 576 mg pyrethrin/system
Step 5: Compare application concentration to LC50 of your system.
576 mg pyrethrin/system is much larger than the LC50 value for a 2,000-gallon system (10.61 mg/
system from step 2). This means that this product is NOT a good choice for application.
Example 2: Azadirachtin – active ingredient in AzaMax Biological Insecticide,
Miticide, and Nematicide
Step 1: Determine the LC50 value from the chemical’s SDS sheet – 4 mg/L (96 hours) for rainbow
trout.
Step 2: Determine the LC50 value for your system. Take the volume of your system in liters and
multiply it by the LC50 (96 hr) value. Let’s use a 2,000-gallon (7,580 L) system as an example.
7,580 L/sys. X 4 mg/L mg/L = 30,320 mg/system
Step 3: Take the pyrethrin concentration and determine how much pyrethrin is being mixed.
The label recommends mixing 1–2 fluid ounces of AzaMax with every gallon of water in compressed
sprayers, which is between 2–4 Tbsp/gallon. In a 2,000 gallon system, the entire crop can be sprayed
with 0.75 gallons of mix, which at the highest application rate is around 3 Tbsp (or 1.5 fluid ounces).
The label tells us that the product contains 0.35 g of azadirachtin per fluid oz. Convert g to lb:
0.35 g azadirachtin/ounce ÷ 454 g/lb = 0.0007716 lbs pyrethrin/fluid ounce
0.0007716 lbs pyrethrin/fluid ounce X 453,592 mg/lb = 350 mg pyrethrin/fluid ounce
Step 4: Determine how much pyrethrin is being applied to the system.
1.5 fluid ounces/system X 350 mg pyrethrin/fluid ounce = 525 mg pyrethrin/system
Step 5: Compare application concentration to LC50 of your system.
525 mg pyrethrin/system is much smaller than the LC50 value for a 2,000-gallon system 30,320 mg/
system from step 2). This means that this product is SAFE to use in your aquaponic system. Even if a
product is generally safe, limiting exposure to the water and organisms is still critical.
Common Pests
Mites: Mites are a very common pest, affecting hundreds of plants. These small arthropods are very small,
often measuring less than 1 mm in length, and have sucking mouthparts. Damage to plants by mites
includes brown stippling on leaves, upturned leaf margins, stunted plant growth, and webbing between
plant structures (spider mites). Symptoms can mimic those of viral infections, particularly those caused by
the broad mite, so identification should be done under a microscope. Mites typically have a 10-to-14 day
life cycle and thrive in dark, humid conditions. Treatment options include neem oil and predatory insects
such as ladybird beetles, lacewings, pirate bugs, predatory thrips, mites, and big-eyed bugs. Common types
include Spider mite, Broad mite, Russet mite, and Cyclamen mites.
Aphids: A primary nemesis of most vegetable gardeners and plants, aphids can be very destructive to
plants. Aphids are typically pear-shaped with two tail-like protrusions at the bottom of their abdomen
(Figure 19a). The life cycle is very short, ranging from 10 days to three weeks. Their reproduction capacity
makes them a particularly hard insect to control. Aphids can reproduce sexually or asexually and can
switch between the two depending on the environment (Van Emden and Harrington 2017). Most aphids
34
35
are born pregnant. Females will either create daughter clones that produce both male and female offspring,
leading to sexual reproduction and eventually egg deposition, or female aphids will simply create live birth
clones of themselves without the help from males. Female clones can survive the winter and continue the
cycle by creating more clones.
Aphids are commonly found in colony clusters on new growth, base of buds, and on the underside of
leaves. Feeding occurs through rasping mouth parts that drain essential nutrient and glucose from the
phloem. As a result, leaves of plants infested with aphids often look shriveled, discolored, or stunted.
Aphids excrete a substance called honeydew, a sugar-rich, sticky liquid that attracts ants. The ants protect
aphids from predators.
Luckily, ladybird beetles (ladybugs) are natural aphid predators. Other treatment options include avoiding
high nitrogen levels, physically removing aphids with a strong spray of water, applying a soap-water
solution to plants, and applying of neem oil (Flint 2013).
Caterpillars: Caterpillars, the larval stage of butterflies and moths, can demolish leafy crops within a short
window (Figure 19b). Their voracious eating habits make them one of the most significant agriculture
pests. Adults feed on pollen nectar and are not a danger to plants; however, if you see adults, you likely
have caterpillars as well. A caterpillar causes leaf damage that appears as holes or large missing section.
Frass, or fecal deposits, appear as small brown/black pellets and are present near damaged tissue.
Common pests include cabbage looper and cabbage worms (Figure 19c) on Brassica sp., cutworms (Figure
19d), diamondback moths (Figure 19e), hornworms (Figure 19f), beet armyworm (Figure 19g), and
inchworms (Figure 19h).
FIGURE 19a
Aphids
FIGURE 19b
Leaf damage due to caterpillar
FIGURE 19c
Cabbage worm
FIGURE 19d
Black cutworm
FIGURE 19e
Diamondback Moth
FIGURE 19f
Hornworm
FIGURE 19g
Beet armyworm
FIGURE 19h
Inch worm
FIGURE 19i
White flies
36
Common treatments include hand removal, B. thuringiensis (Bt), assassin bugs, and lacewings. Chemical
application is not recommended, as it is often more damaging to beneficial insects than target pests and
leads to chemical resistance.
White flies: White flies are sap-sucking insects that are significant pests in a wide variety of vegetable crops
(Figure 19i).
There are three primary whitefly species that impact vegetable crops in the U.S.: the sweet potato,
greenhouse, and the banded-winged whitefly (Natwick et al. 2016). Adults of these species are small (1.52
mm) with yellow bodies and wings covered in a white, waxy powder. Most life stages are found on the
undersides of leaves, where the adults and nymphs feed. Commonly affected crops include beans, broccoli,
cabbage, cauliflower, cucumber, eggplant, melon, peppers, squash, tomato, and watermelon.
Plants with heavy infestation levels may appear stunted, have yellowing or silvering of the leaves, and have
defoliation resulting in reduced yields. Honeydew, excreted during feeding by whiteflies, can reduce the
quality and marketability of vegetable crops. Perhaps the most damage caused by whiteflies is their role as
a vector for more than 100 different plant viruses.
Natural enemies can be effective in reducing or controlling pest levels in greenhouses. Common biological
controls are predators (lacewings, bigeyed bugs, lady beetles), parasites (specifically Encarsia formosa,
a parasitic wasp), and fungal entomopathogens. Insecticidal soaps and oils can provide some control of
whiteflies, but active compounds must cover the undersides of leaves where the insects hide.
Thrips: Thrips are tiny narrow insects that are a common and persistent
pest of vegetable crops in both greenhouse and outdoor systems (Figure
19j). Of the hundreds of species affecting vegetable crops, the Western
Flower thrip and the Onion thrip are the most pervasive. Thrips, like
other insects mentioned here, are sucking insects that drain water and
nutrients from the leaves, leaving them discolored with silvery feeding
scars and wilting of plant components.
All life stages may be damaging, as eggs are commonly laid inside plant tissue, leaving a scar. Typically, the
larval and adult life stages are going to be the most damaging due to plant feeding behavior and the risk of
transmitting viruses to the plant. Thrips complete their lifecycle in 3-5 weeks.
Thrips can be hard to see directly on the plant, depending on the species. Shaking the leaf over a white
piece of paper can help make them more visible. Treatment options vary according to species. Biological
controls include lacewing larvae, pirate bugs, and predatory thrips.
Management of the culture environment and prevention is key to preventing thrips. Use of sticky traps
placed at the base of plants or examination of the underside of leaves for feeding scars are ways to monitor
for presence of thrips. Thrips can be prevented by using proper sanitation protocols for culture equipment,
only using seedlings grown in-house, and preventing weedy areas or overgrown vegetation near the plants
or greenhouse.
FIGURE 19j
Thrips
37
Chemical applications can be effective at treating thrips however most treatments do not kill them outright
and instead prevent them from feeding and thus starving the insect. Due to their lifecycle stages that exist
within the plant, multiple applications may be necessary to eliminate them from the system or control an
outbreak.
A more comprehensive overview of vegetable pests can be found at:
https://entomology.ca.uky.edu/ent60
https://www.uvm.edu/~entlab/Greenhouse%20IPM/pestsandbiocontrols.html
https://content.ces.ncsu.edu/insect-and-related-pests-of-vegetables
Disease Problems and Management
Fish Disease and Treatment
Fish culture is inherently a messy business. Bacterial pathogens and parasites that affect fish are naturally
occurring and opportunistic by nature. Good management, proper husbandry practices, and daily
observation of fish can prevent many issues associated with fish health. Proper management techniques in
the fish production of the aquaponics system should include: system design, water quality monitoring and
correction, equipment maintenance, feed storage, fish observation to remove sick or dead fish, and worker
sanitation. Common external physical signs of fish disease include:
• Hemorrhage: an abnormal discharge of blood
• Lesions: a defined area of diseased tissue such as an ulcer, blister, or canker
• White spots or pustules
• Pale or swollen gills: often seen with fish “gulping” at the surface of the water for air
• Dark coloration
• Excess mucus on the skin or gills
• Sloughing of skin
• Emaciation
• Distended abdomen
• Exophthalmia: pop-eye
There are four major groups of pathogens related to fish culture: fungi, bacteria, viruses, and parasites.
Common fish diseases and their treatment are listed below. Typically, diseases seen in aquaponic
production systems are a result of environmental or physical stress (Figure 20). Stress can stem from 1)
rough or excessive handling, 2) confinement of non-domesticated species of fish into tank systems or
inappropriate stocking densities, 3) improper feed supply, feeding regiment, or nutrition and 4) poor or
unsuitable water quality conditions.
FIGURE 20
Factors leading to fish disease
38
In preparation for stocking fish, biofilters must be broken in (populated with established bacteria before
fish are stocked in the system) and water quality parameters must be within acceptable ranges for the
species of fish being cultured. Once fish are on-site, and before they are stocked into new or existing
production, they should be quarantined and treated prophylactically for external parasites using salt,
formalin, potassium permanganate, or other approved treatments. Treatment must happen outside of the
production system, as chemicals introduced in the aquaponic system will cause the biofilter to crash and
the whole process will have to be started over. Fish should also be observed for any physical abnormalities
in appearance or behavior. Many diseases are first detected by observing abnormal swimming patterns.
Signs of abnormal behavior include whirling, flashing, bobbing, gasping, or side-swimming. Quarantine
facilities and general good fish-handling protocols should include 1) washing hands before and after
interaction with tanks, equipment, feed, or fish, 2) using nets and other equipment only in the quarantine
or production area, 3) thoroughly drying or even bleaching between uses (via bleach buckets or spray
bottles) to kill bacteria, fungus, and parasites, and 4) working in quarantine areas as the last task of the
day to prevent cross-contamination. Arthur et al. (2008) provide a comprehensive overview of quarantine
procedures for live aquatic animals.
Once fish have been stocked and the system is in operation, it is critical that water chemistry be conducted
regularly and that resultant numbers are checked as acceptable for both fish and plants. Any necessary
adjustments should be made as soon as issues are identified, as water chemistry problems will not selfcorrect. Early detection and intervention is the best measure to make sure that production is maximized
for both time-to-market and crop yield.
During production, fish that are crowded into tanks for intensive culture can get stressed, which is
manifested several ways. Stressed fish can go off feed (stop eating); hit the sides of tanks, causing abrasions
to their body or fins; nip at each other in aggression; and even jump out of tanks, resulting in death.
Stressful culture conditions weaken the fish’s immune systems, leaving them more susceptible to bacterial
and fungal infections. Typically, at the first sign of illness, fish will stop eating. At this point, medicated
feed is useless, and a chemical treatment is required.
Another way fish become diseased through stress is poor water quality conditions. This can be a result of
poor water chemistry and inadequate water conditions. For example, fish become stressed during acute
or chronically low levels of dissolved oxygen and are more susceptible to disease. Another example is
occasional overfeeding of fish. The excess protein breaks down into total ammonia-nitrogen, which breaks
down further into toxic components of un-ionized ammonia-nitrogen and nitrite-nitrogen. The biofilter
component is not sufficient to convert these compounds to nitrate, leading to stress on the fish from poor
water quality. These toxic components are further exacerbated by issues such as high pH and increasing
temperatures.
To prevent stress on the fish, a general rule of thumb is to stop or reduce feed input in the system:
• When temperature is outside of species range
• When fish are sick or stressed
• 24-48 hours before/after transport
• 24 hours before sampling
• 3-4 days before processing
• When low DO is present
• When water quality parameters are sub-par
If fish stocked into production become sick, they should be removed from the system immediately for
treatment or disposal. Water amendments should be made promptly, stocking rates should be checked,
water flow should be checked, and water exchanges may be necessary. There are no good treatment options
for treating systemically in production, as chemicals cannot be used with coupled aquaponic systems. Fish
can be removed or isolated, treated in containment, and reintroduced at a later date.
System design plays a role in disease prevention. Tanks used for fish culture should be round and
preferably have a conical bottom for removal of settle-able solids. Design should be such that tanks are
easy to disinfect, can be isolated individually from the rest of the system, and have windows to view fish in
the water column.
Common Fish Diseases and Their Treatment
Parasites
Ich (white spot disease): Ich is caused by the parasite
Ichthyophthirius multifiliis (Ich). Ich appears on infected fish
as small white specks on their skin and/or gills (Figure 21a).
Fish may exhibit “flashing” behavior, characterized by a quick
rubbing or scratching movements against the tank bottom,
wall, or surface of the water (Durborow et al. 2000). Excess
mucus is commonly present; however, the only clear sign may
be a dead or dying fish. Treatment for Ich is difficult; however,
elevating water temperature to above 85°F can kill Ich by
disrupting its life cycle. Chemical treatments for quarantine
tanks or decoupled systems include multiple treatments of
formalin, copper sulfate (CuSO4), or potassium permanganate
(KMnO4). Check appropriate dose rates before administering.
These chemicals should not come into contact with plant
components and must be administered in an isolated tank.
Simply harvesting the fish may be the simplest solution.
Whirling disease: Caused by Myxobolus cerebralis, whirling
disease primarily infects salmonids (trout and salmon) and can
enter the aquaculture system through affected fish. Symptoms
include abnormal swimming, darkening of posterior part,
and skeletal deformation (Idowu et al. 2017). There is no true
effective treatment for whirling disease. Producers should only
purchase salmonid fingerling from hatchery that are certified
whirling disease free and use treated water or ground water for
production.
Bacterial Infections
Columnaris: Infections from Flavobacterium columnare are
common in aquaculture-reared fish. Common symptoms
include red or pale ulcers on the skin; yellowish mucus on
39
FIGURE 21a
Ich
FIGURE 21b
Columnaris
FIGURE 21c
Aeromonas
40
the skin, gills, and/or mouth; and necrosis/erosion of the gills. Saddleback is a common lesion caused by
columnaris and appears as a pale white saddle-like band encircling the body (Figure 21b). The bacteria
can cause disease under normal culture conditions, but more likely when fish are stressed by low oxygen,
high ammonia, high nitrite, high water temperatures, rough handling, mechanical injury, and crowding.
(Durborow et al. 1998). Columnaris is typically treated with chemical treatment of the water using
KMnO4 or by using Terramycin® (oxytetracyline HCl). Medicated feed that contains the antibiotics
Aquaflor®, Terramycin® or Romet® may be effective. Chemical treatments or antibiotic feed should not
come into contact with plant components and must be administered in an isolated tank.
Aeromonas: Aeromonas is a genus of bacteria that is widespread and is commonly isolated from
freshwater culture environments. The disease caused by these bacteria in fish is called Motile Aeromonas
Septicemia (MAS) (Hanson et al. 2019). Aeromonas infections are probably the most common bacterial
disease diagnosed in cultured warmwater fish. Fish with septicemia often have hemorrhages (red areas or
spots) on the skin, eyes, and fins; a dis¬tended abdomen; flared scales due to edema in the scale pockets
(dropsy); and/or a red, inflamed anus (Figure 21c). Internally, the muscle and visceral tissue are often red,
and the body cavity may contain bloody fluid. Typical MAS can be attributed to a predisposing factor,
such as a handling event, temperature shock, water quality stressor, spawning, or aggression. Treatment
is currently limited to three antibiotics: Aquaflor®, Terramycin® and Romet®-30. Proper withdrawal times
for each antibiotic must be observed before treated fish can be processed/harvested. Chemical treatments
or antibiotic feed should not come into contact with plant components and must be administered in an
isolated tank.
Enteric Septicemia of Catfish (ESC): ESC is also known as “Hole-in-Head Disease” and is caused by the
bacteria Edwardsiella ictaluri. It most commonly affects catfish species and is accountable for one-third of
reported fish diseases in the southeastern U.S. Behavioral signs of infection include head-chasing-tail or
whirling rather than swimming, as well as “star gazing.” External signs include red or white shallow ulcers,
a hole appearing in the top of the head, and fluid buildup in the abdomen, causing severe distension.
Treatment is typically administering medicated feed containing the antibiotics Aquaflor®, Romet®, or
Terramycin®. Chemical treatments or antibiotic feed should not come into contact with plant components
and must be administered in an isolated tank.
Viral Infections
Tilapia Lake Virus (TiLV): TiLV is one of the only significant viruses that affect tilapia in both wild and
cultured situations. It is caused by Tilapia tilapinevirus and has been seen in Asia, Africa, and South
America. It is transferred quickly through infected populations, and there is no treatment at the time of
this publication.
Plant Disease and Prevention
Plant disease problems can be difficult and time consuming to treat. Preventing issues from arising is the
first step in proper plant care. Many foliar plant diseases are present during conditions of high temperature
and humidity. Providing proper ventilation and reducing humidity will prevent conditions that allow mold
and disease to spread to other plants.
Plant nutrition plays a direct role in disease resistance in plants (Agrios 2005). Providing the correct
balance of nutrients is important not only for growth but also to decrease susceptibility and increase
recovery from certain plant disease. Table 10 describes the role of certain nutrients for prevention of plant
disease. Below are common plant diseases in aquaponic systems.
41
Bacterial canker: The bacteria that causes bacterial canker, Pseudomonas syringae,
enters the plant through existing wounds caused by pruning, harvesting, or injury.
Signs of bacterial canker include marginal browning or necrosis on leaves, elongated
tan regions or splitting of the stem, and/or small white spots on the fruit (Figure
22a). The most common cause is unsanitary growing condition or harvesting tools.
Grey mold: Caused by the pathogenic fungus, Botrytis cinerea, grey mold can be
found almost anywhere plants are grown. Prevalent during damp, cool weather, grey
mold can spread quickly through the crop, affecting stems, leaves, and fruits. Leaves
may have brown lesions that spread over the entire surface, causing the leaf to wilt
(Figure 22b). If not controlled, spores will spread to flowers and fruits, where fuzzy,
grey growth will appear (Figure 22c). Improving ventilation with fans and air flow
within the plant structure through pruning are preventative measures. In addition, removing fallen or
diseased plants and avoiding injury to trellised plants is critical in preventing grey mold.
Powdery and downy mildew: These two types of mildew affect nearly all vegetable crops. Primarily
affecting the leaves of the plant, they are more prevalent in humid conditions. Powdery mildew is circular
and white in appearance and can appear anywhere on the leaf surface. The leaf may yellow if the fungus
has been present for a long time. A downy mildew spot is angular and grey in appearance and the fungus is
limited by the leaf vein. Leaves may appear yellow before the presence of the fungus is evident (Figure 22d).
Table 10: Role of nutrition in plant disease resistance.
Nutrient Effect
Nitrogen Overfertilization makes more succulent tissues that are more prone to fungal attack. Nitrogen starvation
results in stunted plant that are more prone to attack from opportunistic micro-organisms.
Phosphorus Improves nutrient balances and accelerates maturity of the plants.
Potassium Accelerates wound healing and reduce the effect of frost damage. Delays maturity and senescence of plants.
Calcium Reduces the severity of some root and stem fungal diseases. Affect the cell wall composition in plants that
resist fungal penetrations.
Silicon Helps plants produce specific defense reactions, including the releases of phenolic compounds against
pathogens.
FIGURE 22b, c
Grey mold.
FIGURE 22d
Powdery and downy mildew on grape leaf.
FIGURE 22a
Bacterial canker in leaf.
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Pythium: The causative agent for root rot in plants, Pythium
sp. are found naturally in the culture environment and impact
a wide variety of plants. Symptoms include brown, rotting
roots that slough off easily when disturbed (Figure 22e). Plants
may appear stunted or nutrient-deficient. Different species
of Pythium are prevalent at specific temperatures; however,
in aquaponics they commonly appear at water temperatures
above 78°F and conditions with high organic solids. Controlling
temperature and implementing effective solids removal will limit
Pythium sp. in an aquaponics system.
Steps to Prevent Plant Disease
in Aquaponic Systems:
• Control temperature and humidity of the growing environment. High temperature and humidity
often are the ideal environment for growth and spread of fungal and bacterial disease in plants.
Particularly in a greenhouse or indoor facility, forced air ventilation and prevention of evaporation will
reduce these parameters. It is also important to control these in and around the plant structure. This is
accomplished through appropriate plant spacing and pruning fruiting crops with dense foliage.
• Sanitation. Implementing sanitation standard operating procedures (SSOPs) will help prevent disease
outbreak in vegetable production units. Sanitizing propagation and harvesting tools and growing
equipment such as rafts and NFT channels will also help prevent disease outbreak.
• Remove dead or diseased plants. Prompt removal and disposal of affected plants can help the spread of
disease in the facility.
• Choose appropriate plant species. If external environmental conditions cannot be controlled,
choosing resistant or appropriate varieties will save practitioners time and money.
• Seed quality and storage. Buy quality seeds and store them under refrigeration to prevent the seeds
from molding and to increase germination.
Food Safety and Sanitation
Sanitation and cleanliness of an operation is critical to ensure Good Agricultural Practices (GAP)
regarding food safety (Hollyer et al. 2012). This is important because as of 2018, the CDC estimated that
each year, 48 million people get sick from a foodborne illness, 128,000 are hospitalized, and about 3,000
people die. If the aquaponics industry wants to become a larger part of global food production and the
fresh-cut sector, it is critical to maintain a good reputation and positive public perception of food safety for
both fish and plants cultured within the same system.
The largest food safety concern within aquaponics is the spread of zoonotic pathogens (E. coli, salmonella,
etc.), which can be present in harmful quantities within the water. The contamination can happen from
people contacting the water or from consuming plant leaves that have been in contact with the aquaponic
water (Hollyer et al. 2012). Analyzing water and plant samples annually will help producers build a strong
understanding of potential sources of contamination.
Prevention is the best tactic for biosecurity and food safety, which is why every aquaponics operation
should have SSOPs (Sanitation Standard Operating Procedures) and follow the seven principles of
HACCP (Hazard Analysis and Critical Control Point). SSOPs are written rules for food processing that
FIGURE 22e
Pythium on lettuce roots.
43
an operation develops and implements to prevent any contamination of their tools or production space.
HACCP dictates the maximum/minimum values to which biological, chemical, or physical parameters
must be maintained at a critical control point to prevent food safety hazards. Examples of sanitation
procedures to eliminate the spread of disease, pests, and food safety issues for both fish and plants include:
• Annual pathogen and bacterial tests
• Continuous improvements to SSOPs and HACCPs
• Overall production space cleanliness and biosecurity
• Tool sanitation
• Human sanitation
• Sanitation education
• Proper food storage
Sanitation is especially important when considering that most aquaponics systems are recirculating, and
what is normally done in recirculating aquaculture to treat sick fish cannot be done easily in recirculating
aquaponics due to the integrated plant production. Therefore, a net dip should be present on-site
to prevent the spread of fish pathogens through fish contact with a contaminated net. Virkon is one
example of a fish-safe net sanitation product that can be applied to a net according to the manufacturer’s
instruction. Keeping tank rims clean of uneaten fish food is a simple way to reduce potential fungus and
pest growth. Monitoring and maintaining feed quality will reduce risks associated with fish getting sick
from ingesting moldy food.
Creating and following a detailed plan of how fish
and plants are processed will drastically reduce
food safety concerns. Fish processing requires
producers to follow strict HACCP regulations
and inspections, which is prohibitive to most
aquaponic producers due to the amount of fish
per harvest and overhead costs associated with
fish processing. Therefore, many aquaponics
farms will sell whole fish either live or on ice.
Fish processing regulations may vary from state
to state. Plant processing will be regulated by
SSOPs, which will include washing hands before
harvesting or after touching water; washing tools
in soap or diluted bleach solution; maintaining a
clean harvest area; and cleaning rafts/grow media
with disinfectants (soap, hydrogen peroxide, etc.)
(Figure 23).
Potential hazardous foods (PHF) are foods that
will spoil, causing food safety issues, if kept at
room temperature for certain amounts of time
(Busta et al. 2003).This would include both fish
and plants (vegetables, microgreens, fruits)
produced within aquaponic systems. Improper
cooling of foods is the number one cause (>30%)
FIGURE 23
Sanitizing harvesting tools
44
of foodborne illness. Time and temperature are the two factors influencing food spoilage the most.
Humidity of the storage environment and equipment will also impact food shelf life. Microgreens and
sprouts are especially of concern when considering food safety, as they require no processing or heattreatment prior to consumption and have a shorter shelf life, making them more susceptible to bacterial
spoilage.
Utilizing education, training, and readily available information for employees about food safety practices
is the best strategy for prevention. Signs reminding employees to maintain cleanliness can also help.
Additionally, educating employees on where the highest risks of food safety contamination can occur
within any operation is key. Cost implications food safety procedure and compliance should be included
within a budget.
45
IX. Controlled Environment Growing
Types of Greenhouses
Free-standing greenhouses come in a variety of shapes and sizes (Figure 24). Choice of greenhouse
depends on snow load and wind speed of a particular location. Free-standing greenhouses are less
expensive than larger structures and are easier to optimize
environmental parameters for different crop species. If multiple
stand-alone structures are used, increased sanitation protocols
are required to prevent insect pest and disease issues from being
transferred between structures by workers.
Gutter-connected greenhouses provide a more efficient use of space
and reduced overall heating costs during winter compared to standalone structures (Figure 25). The upfront cost of this greenhouse style
is high and may be cost prohibitive for growers on a limited budget.
Lean-to greenhouses have one wall that borders a building. Light
reduction is not severe if the dark wall is the north wall. These types
of structures may be useful for decoupled aquaponic systems, as
environmental parameters can be controlled independently in each
structure.
Greenhouse Covering Options
Greenhouse coverings come in a variety
of materials, including glass, rigid plastic
(fiberglass, polycarbonate, or acrylic), and
plastic films. The appropriate choice depends
on your climate zone and budget. Regions
with a colder climate will require the covering
to provide increased insulation and low heat
transfer measured by the R-value and U-value,
respectively. The R-value measures how well
the material insulates. The higher the R-value,
the more insulation the material provides. The
U-value quantifies heat transfer and describes
how much heat is lost or gained. Materials with
a lower U-value will be more energy efficient.
Approximately 75% of plastic used for covering
greenhouses in the U.S. is air-inflated doublelayer polyethylene plastic. 6ml polyethylene plastic covering is inexpensive and has an R-value of 1.4
and a U-value of 0.5 (high insulation capacity and energy efficient). A single layer fiberglass covering is
moderately expensive and has an R-value of 0.83 and a U-value of 1.2 (moderate insulation capacity and
not energy efficient) (Table 11). Choosing the right material for your climate zone is critical to reduce
heating costs during winter. Energy cost is the second greatest production expense, just behind labor.
FIGURE 24
Different styles of greenhouses
FIGURE 25
Gutter connected greenhouse
46
Heating and Cooling Options
Heating: For small or backyard-size
producers, implementing a passive
heating system can help reduce heating
costs during cold months. In this type of
system, sunlight enters the south wall. The
north wall has reflective material to trap
and store heat. Black barrels filled with
water absorb heat from sunlight during
the day and slowly release the heat during
the night. Thermal curtains can be hung
on the south wall to trap heat during the
night (Figure 26). While helpful to reduce
heating costs, this practice would not be
practical for large producers as it takes up
valuable production space in the facility
and is not able to maintain a consistent and reliable temperature.
Larger producers that have year-round, consistent production will need to maintain a
temperature independent of what can be gained from the sun. Forced air heaters powered by
natural gas, propane, or electricity are most commonly used in the U.S. These heaters control the
air temperature by a thermostat. Radiant heaters such as wood or natural gas broilers control the
temperature by pumping hot water through pipes located throughout the structure. Broilers are
popular, as wood is a cheap source of fuel compared to oil or natural gas.
FIGURE 26
Passive solar greenhouse
Table 11: Comparison of greenhouse glazing materials.
Material Life R value U value Advantages Disadvantages Cost
Glass
Single layer, tempered
(Until it
breaks)
0.95 1.13 Strong, attractive,
good seal, 90% light
penetration
Breaks, difficult to install,
heating
$$$
– $$$$
Rigid plastics
Fiberglass
6-15
years
0.83 1.20 Lightweight, strong,
light penetration
Opaque, degrade/yellow
over time-6yrs, needs
resin recoat
$ – $$
Rigid single-wall $ – $$
Rigid double-wall acrylic 20 yr 1.4-1.9 0.75-1.0 Transparent, 30%
energy savings with
double layer, Bends
Extra layer reduces light
pentration to about 80%
$$ – $$$$
Rigid double or triple
wall polycarbonate with
UV coating
10-15 yr 1.4-1.9
Triple 2.5
0.53-0.70 Same as acrylic, may
bend more easily than
acrylic
Same light as acrylic, but
will yellow without UV
coating, about 80%
$$ – $$$$
Plastic films (rolls)
Single layer, 6 ml
1-4 yr .85 1.20 Good light penetration
(90% 1-layer)
inexpensive
Needs to be replaced
frequently, condensation
$
Double layer, 6 ml
(polyethylene)
1.4 0.5-1.0 Reduces
condensation,
increases warmth
Reduces light 10& with
each layer (80% total)
$
47
Cooling: The combination of manual
and automatic ventilation is the most
cost-effective way to cool down your
greenhouse. Ventilation options include
roll-up sides, ceiling vents, and vents
along the long end of the greenhouse.
Forced air ventilation fans pull air
through the length of greenhouse using
thermostat-controlled vents at the
opposite end. Evaporative coolers are
a relatively inexpensive way to provide
cooling to the structure in hot, dry
climates. Evaporative coolers work by
pulling in outside air through a wet
wall, cooling the air as it comes in.
The wet wall is a frame that contains
corrugated cardboard or synthetic
material that is saturated by water dripping over its surface (Figure 27). Excess water is collected
in a reservoir and pumped back over the cardboard. Evaporative cooling walls are not efficient in
climates with high temperature and high humidity.
Indoor Production
Moving production into an insulated
building is suitable for producers who want
to be close to urban markets, have a lack of
arable land, or live in a climate not suitable
for outdoor or greenhouse production.
No matter where a plant is grown, it still
requires optimal conditions to reach its
maximum yield potential. In addition to the
controls discussed above, producers must
also provide light suitable for optimal plant
growth. For plants, light stimulates seed
germination, food production, flowering,
chlorophyll manufacturing, and branch and
leaf thickening.
Photosynthesis is stimulated by the type and frequency of light received. Light is emitted as waves of
photons, or bundles of energy. The amount of energy in each photon determines the length of the wave
from crest to crest. Lower energy wavelengths emit a blue light (400 nm) and higher energy wavelengths
emit a red light (700 nm). Plants utilize wavelengths between 400-700 nm. Blue and red light is required
in different ratios at different periods in the plant’s life. Blue light is primarily responsible for vegetative
growth. Red light triggers cell elongation, vegetative growth, and flowering.
FIGURE 27
Evaporative cooler
FIGURE 28
Plant growth under LEDs
48
Traditional plant grow lights are fluorescent (FL) or high intensity discharge (HID) fixtures. Compact T5,
T8, and T12 FL bulbs are mainly used for seed propagation or vegetative growth. HID fixtures are often
sold to accommodate both metal halide (MH) and high-pressure sodium (HPS) bulbs. Light produced by
MH bulbs is the 400-550 range, suitable for vegetative growth. Light produced by HPS bulbs provide light
in the yellow, orange, and red spectrum, more suited for flowering and fruiting stages. Both FL and HPS
bulb have a lifespan of 20,000+ hours and generate a considerable amount of heat.
Advances in plant grow lights have made indoor production more cost effective through improved energy
efficiency and higher plant yields. Induction fixtures (IND) are similar to FL bulbs but have become more
popular, as they have no electrodes allowing them to last considerably longer (75,000+ hours). They also
put off much less heat and are more energy efficient. Light emitting diodes (LED) lights were once too
expensive for many growers; however, they are now considered the standard for plant grow lights. LED
lights operate by passing an electrical current through two semi-conductors (one positive, one negative)
which then emit light. The spectrum can be dialed into what is required by the plant at different stages,
improving the quality and yield of the crop. In addition to improved energy efficiency, LED lights have a
lifespan of 100,000+ hours.
Research conducted at Kentucky State University compared growth of six leafy greens and energy use
for FL, MH, IND, and LED grow lights. LED lights produced significantly higher plant biomass (g/m2)
compared to the other three lights (Figure 28: KSU unpublished, Oliver et al. 2018). As the cost of LED
lights continue to decrease, production costs for indoor plant production will also decrease.
49
X. Marketing and Economics
Economic
There is relatively little information available on the economics of aquaponics, likely due to a lack of
successful commercial production before 2014. Based on information summarized in Engle (2015) and
Heidemann and Woods (2015), aquaponics profitability is achievable depending on geographic location,
climate, initial investment, production cost, market demand, and consumer preference for goods.
Production in USDA Zones 7-13 are typically most profitable in the U.S. due to reduced risk of losses
associated with cold weather, power outages, and utility costs (Love et al. 2015). Another production
factor is labor costs, which have been estimated at 46% of total operating cost and 40% of total annual cost
(Tokunaga et al. 2015). Reduced delivery travel costs are associated with aquaponic production due to the
capability of suburban and urban production.
An international survey of aquaponic growers found a significant relationship between sales of non-food
products from aquaponics farms (i.e. training, workshops, system designs, consulting services) and the
farms’ profitability (Love et al. 2015). Crops grown in aquaponics can be very profitable; however, several
studies have shown that the fish component is far less so. But while the crops may produce a larger profit
than the fish (and the amount of space/area devoted to fish in the aquaponics system may be minimized),
the “advertising-value” of the fish has a worth that exceeds the actual dollar amount brought in from fish
sales. This may be even more true with systems located in the Virgin Islands and Hawaii that experience
long, consistent daylight hours with little daily temperature fluctuation and where the price of fresh
produce is very high.
Considering the inherent adaptability of aquaponic production, potential success should be carefully
weighed from available information, a well-constructed business plan, and individual needs and inputs.
An operating plan should include, but not be limited to, the investment required to construct facilities and
purchase equipment, annual costs to operate the system, projections of market prices and competition,
and realistic estimates of potential revenue. Based on information from three commercially surveyed
aquaponic farms, the estimated payback period can be between two to five years.
Marketing
The most difficult aspect of any aquaponics operation is developing a realistic and practical marketing
scheme (Engle 2015). Location is key for marketing because location determines what is in demand and
the size of the market. Having close access to multiple cities significantly increases the market size as well
as market demographics and in turn increases demand for product. If the location is within a remote area
such as an island, then the market price for the product will be much higher compared to a location in an
easily accessible area (Engle 2015). Since aquaponics production can be done year-round, growing and
selling produce that is locally considered “out of season” can help achieve a higher price point. Offering a
variety of niche crops such as microgreens, house plants, and herbs holds much potential to increase the
market as well as profits.
In order to enhance the marketability of aquaponic produce, certain certifications will be extremely
helpful. These certifications include organic and certified naturally grown (CNG). In order to maintain
50
the organic label, extra funds will need to be used in order to satisfy the regulations, but overall the
product will be able to be marketed as a high-quality product, raising the price consumers are willing
to pay. The other option is to be certified as naturally grown, which means no synthetic chemicals are
used in the operation, which stands true for most aquaponic farms. While organic is still the word most
consumers know, being certified as naturally grown can still draw in top-dollar prices that consumers are
willing to pay. No preservatives! No pesticides! No herbicides! Local! Homegrown! These are also labeling
strategies that can be used to promote the sale of aquaponic produce. Clever and catchy labeling that is
easily spotted in stores can help leave an impression in a consumer’s mind about the product. Just having
aquaponic-grown fish available from a business will make their hydroponically-grown crop more desirable
to environmentally-conscience customers, so even though fish may be a small percentage of what the
business produces, it serves as a “marketing tool” for all other sales from that business.
Selling directly to restaurants, farmers markets, and CSA markets has potential to generate more revenue
compared to selling it wholesale. These routes allow for a closer personal contact with the consumer and
allow the aquaponic producer to tell their story. Although wholesale can be much more reliable and easier
to work with, the profits are drastically reduced, since the price of the product is sold at a much lower
price. Selling wholesale also requires a much larger capacity than what most aquaponics farms have, which
is why selling directly to the consumer is typically the market chosen for business.
51
XI. Certifications and Regulations
Organic Certification
Organic food sales in the United States rose by 5.9% in 2018, totaling $47.9 billion dollars. It is no surprise
that aquaponic farmers want the organic label to bolster their marketing and sales, and equally no surprise
that soil-based farmers do not want their selling power to be diluted. The heart of organic production
is cultivating soil, so how can produce be certified organic if there is no soil? In 2015, a taskforce was
assembled consisting of individuals representing both the soil-based organic industry and the hydroponic
and aquaponic communities. The goal was to describe hydroponic and aquaponic systems and practices,
examine how hydroponics and aquaponics align or conflict with USDA organic regulations, support their
decisions with science, and explore alternatives. At its 2017 fall meeting, the National Organic Standards
Board (NOSB) voted 8-7 against a proposal to prohibit hydroponic and aquaponic production in organic
agriculture. Although aeroponics is prohibited, both hydroponics and aquaponics remain eligible for
organic certification, while the USDA considers the NOSB decision. While aquaponics lends itself to a
more sustainable growing methods, only OMRI approved items can be used during production. This
prohibits the use of rockwool, hydroxide bases, chelated iron, and other common tools of the trade.
Currently, only 17 of 80 certifiers will assist aquaponic farms with organic certification.
Certified Naturally Grown (CNG)
Known as the “grassroots alternative to organic,” CNG certification follows organic standards but
focuses on growers who sell directly to the consumer. CNG farmers are restricted from using synt8hetic
herbicides, pesticides, fertilizers, or genetically modified organisms (GMOs). Farms with CNG
certification undergo an annual inspection and pay an annual fee. Inspections can be conducted by other
CNG farmers, Extension agents, master gardeners, or other qualified personnel. Sections of the CNG
standards for aquaponics can be found at (https://www.cngfarming.org/aquaponics_standards).
Good Agriculture Practices (GAP)
Good Agriculture Practices (GAPs) are specific methods that, when applied to agriculture, create food
for consumers or further processing that is safe and wholesome. Currently a voluntary certification,
the Food Safety Modernization Act (FSMA), will require farms to comply with food safety and security
measures outlined in the document. In 2011, the Produce GAPs Harmonized Food Safety Standards
was released, which require producers to meet standards for biosecurity, sanitation, worker training,
and documentation. Information on Produce GAP can be found at (https://www.ams.usda.gov/services/
auditing/gap-ghp/harmonized).
Hazard Analysis and Critical Control Point (HACCP)
HACCP is a management system in which food safety is addressed through the analysis and control of
biological, chemical, and physical hazards from raw material production, procurement and handling to
manufacturing, distribution, and consumption of the finished product.
Standard Operating Procedures (SOPs) and HACCP
Determining risk factors in the production, processing, sale, and consumption of food items involves
HACCP, SOPs, and Sanitation SOPs (SSOPs). Developing a protocol for each step of the operation and
providing employee training is essential to provide a safe food product. The following are examples of how
HACCP, SOPs, and SSOPs work in conjunction.
52
1. Chemical: Use of cleaner on surfaces. Could it be a hazard? Yes, but in our SSOP we have a second
rinse step to remove residue, so it is not a CCP because it is handled someplace else in the plans.
2. Physical: Knife chips in the roots, cuttings, or fish fillets. Could it be a hazard? Yes, but in our SOPs
in our work flow all knives are inspected at the start of all working and at three-hour breaks, or all
products are passed through a metal detector. So, it is not critical control point.
Best Aquaculture Practices (BAPs)
Based on BAPs, the five pillars of responsible aquaculture are environmental responsibility, animal health
and welfare, food safety, social responsibility, and traceability. Critical requirement include record keeping
and traceability, worker safety and hygiene, and biosecurity. More information on BAPs can be found at
(https://www.bapcertification.org/).
Propagation Permits
Commercial fisheries propagation permits are required by state wildlife agencies for culture and sale of
aquatic organisms. Information provided includes the name and location of the business, water source,
flooding likelihood, discharge information, how the brood stock was obtained, quantity and type of species
produced, and the type of production system. Required information and cost of the permit will vary by
state.
53
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Goddek, Simon, Alyssa Joyce, Benz Kotzen, and Gavin M. Burnell. Aquaponics Food Production Systems
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bitstream/handle/20.500.12657/22883/1007278.pdf?sequence=1&isAllowed=y (Accessed
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Klinger-Bowen, R. C., C. S. Tamaru, B. K. Fox, K McGovern-Hopkins, R. Howerton. 2011. Testing your
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for Tropical and Subtropical Aquaculture Publication. Available: http://www.ctsa.org/files/
publications/TestingAquaponicWater.pdf (Accessed June 29, 2016)
Mischke, C. and J. Avery. 2013. Toxicities of Agricultural Pesticides to Selected Aquatic Organisms.
Southern Regional Aquaculture Center Publication Number 4600. Available: https://sracaquaponics.tamu.edu/serveFactSheet/5 (Accessed June 29, 2016)
Mullins, B. Nerrie, and T. D. Sink. 2015. Principles of Small-Scale Aquaponics Southern Regional
Aquaculture Center Publication Number 5007. Available: https://srac-aquaponics.tamu.edu/
serveFactSheet/9 (Accessed June 29, 2016)
Pattillo, D. A. Marketing Local Foods in Iowa – Seafood. December, 2017. Iowa State University Extension
Publication FS 0018. https://store.extension.iastate.edu/product/15328 (January 10, 2018)
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Pattillo, D. A. and S. K. Rotole. Building and Caring for a Miniature Aquaponics System. October, 2017.
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Pattillo, D. A. and M. Speltz. Iowa Fish Processing Frequently Asked Questions. October, 2016. Iowa State
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Pattillo, D. A. Standard Operating Procedures – Feeding Practices and Feed Management. December,
2014. Available: https://store.extension.iastate.edu/Product/Standard-Operating-ProceduresFeeding-Practices-for-Recirculating-Aquaculture (October 27, 2015)
Pattillo, D. A. Feeding Practices Monitoring Sheet (Sample). December, 2014. Available: https://store.
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extension.iastate.edu/Product/Feeding-Practices-Monitoring-Excel-Sheet (October 27, 2015)
Pattillo, D. A. Water Quality Management for Recirculating Aquaculture December, 2014. Available:
https://store.extension.iastate.edu/Product/Water-Quality-Management-for-RecirculatingAquaculture (October 27, 2015)
Pattillo, D. A. Standard Operating Procedures – Water Quality Management for Recirculating Aquaculture.
December, 2014. Available: https://store.extension.iastate.edu/Product/Standard-OperatingProcedures-Water-Quality-Management-for-Recirculating-Aquaculture (October 27, 2015)
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store.extension.iastate.edu/Product/Water-Quality-Management-Monitoring-Sheet-Sample
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(October 27, 2015)
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Pattillo, D. A. 2014. Aquaponic System Design and Management. Iowa State University Extension.
Available: https://www.extension.iastate.edu/forestry/tri_state/tristate_2014/talks/PDFs/
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Wurts, W. A. and R. M. Durborow. 1992. Interactions of pH, Carbon Dioxide, Alkalinity and Hardness in
Fish Ponds. Southern Regional Aquaculture Center Publication Number 464. Available: https://
srac-aquaponics.tamu.edu/serveFactSheet/4 (Accessed June 29, 2016)
Recommended Videos
Danaher, J. 2015. Aquaponics – An Integrated Fish and Plant Production System. Southern Regional
Aquaculture Center. http://www.ncrac.org/video/aquaponics-integrated-fish-and-plantproduction-system (Accessed June 29, 2016)
Hager, J. V and Dusci, J. 2020. IBC Aquaponics: a step-by-step guide. https://www.youtube.com/
watch?v=BwbvOMoU9oE
Pattillo, D. A. 2016. Aquaponics: How to Do It Yourself! North Central Regional Aquaculture Center
Webinar Series. Accessed: http://www.ncrac.org/video/aquaponics-how-do-it-yourself (Accessed
June 29, 2016)
Pattillo, D. A. 2013. Aquaponics System Design and Management. Iowa State
University Extension. Available: https://connect.extension.iastate.edu/
p5fba9a68a0/?launcher=false&fcsContent=true&pbMode=normal (Accessed June 29, 2016)
Rode, R. Aquaponics. 2013. Available: https://extension.purdue.edu/pages/article.aspx?intItemID=8789
(Accessed June 29, 2016)
Ron, B. T. 2014. Aquaponics: Paradigm Shift with Airlift. eXtension.org. Available: https://www.youtube.
com/watch?v=ZWGs4NIkrLs&feature=em-upload_owner (Accessed June 29, 2016)
Ron, B. T. 2014. Aquaponics: Paradigm Shift with Airlift Pumps Part 2. eXtension.org. Available: https://
www.youtube.com/watch?v=1EDlMqrngqQ&feature=em-upload_owner (Accessed June 29, 2016)
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Shultz, C. Overview of Replicated Aquaponic Systems at Kentucky State University. Available: https://www.
youtube.com/watch?v=gTg3eQZaR5E (Accessed 2/13/2018)
Storey, N. Biological Pest Control for Aquaponics. Bright Agrotech. https://blog.brightagrotech.com/
pesticides-for-aquaponics/ (Accessed 2/13/2018)
Resource Pages
Agricultural Marketing Resource Center http://www.agmrc.org/
Aquaponics Association http://aquaponicsassociation.org/
Aquaponics Journal http://aquaponicsjournal.com
ATTRA National Center for Appropriate Technology https://attra.ncat.org/
Kentucky State University – Aquaculture Research Center http://www.ksuaquaculture.org/
Iowa State University Extension Online Store http://store.extension.iastate.edu/
Iowa State University Fisheries Extension http://www.nrem.iastate.edu/fisheries/
North Central Regional Aquaculture Center www.ncrac.org
Southern Regional Aquaculture Center – Aquaponics Publication Series
https://srac-aquaponics.tamu.edu/
Sustainable Agriculture Research and Education Program http://www.sare.org/
USDA – National Agricultural Library https://www.nal.usda.gov/afsic/aquaponics
University of Minnesota Aquaponics http://www.aquaponics.umn.edu/aquaponics-resources/
Texas A&M Aquaponics http://fisheries.tamu.edu/aquaponics/
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