Module 7 – Plants



In the previous section, we said…

“If you’ve never kept fish before, you may be faintly hesitant at the prospect.


When you operate an authentic iAVs, you are engaging in freshwater aquaculture in its simplest and most cost-effective way.

Freshwater aquaculture has been the subject of many doctorates…and its experts have published many substantial books.

My point is that in a short course like this, we won’t be teaching anything much about aquaculture.

We’ll help you to broaden your aquaculture knowledge and skills over time but, for now, we’ll be focused on showing you how to keep fish growing plants the iAVs way.

We’ll provide close direction so that you can grow as you learn…and learn as you grow!”

The same thing goes for plants…by design.

We can’t begin to teach you horticulture.  The field is huge.

What we will do, however, is show you how to grow plants in an iAVs.

And that starts with putting fish and plant production in an iAVs into perspective.

The aquaculture component provides the fertilizer source materials to be ‘processed’ by the soil organisms. At best, the fish production aspect represents but 10% of the potential production value – most probably less when done correctly.

To clarify it further, the plants are (in value terms) the main game…the end.  The fish are simply the means to the end.

Just so we’re clear, that doesn’t infer anything about keeping fish in poor conditions – or ignoring what value they do have. It’s simply an acknowledgment of the fact that for every kilogram of feed we put into an iAVs – we can expect 0.75kg of fish and around 7.0kg of fruit and vegetables.

The filtration efficacy of sand and the intermittent irrigation regime both contribute to excellent water quality in the iAVs.

If you experience anything other than gin-clear water in the fish tank, you should investigate the cause of the discolouration.

iAVs is ‘organic’ Horticulture.

That’s not a philosophical position…but rather an important financial reality… because in most markets, the organic fruit and vegetables will be worth considerably more than the fish you grow.

By the way, when we talk about ‘plants’ we mean fruiting plants – nutrient-dense food crops.  Leaf crops and herbs are also viable and most profitable when grown as an intercrop around fruiting vines or other slower-growing crops.

If you have little knowledge about gardening – and the conditions that vascular plants need to thrive – then we recommend that you learn – and apply – the cultural best practices associated with the plants that you intend to grow.

In the meantime, some of what follows will be helpful as we get growing.

Plant Species

Let’s begin our consideration of plants with just a few of the species that can be grown in an iAVs. This list is nowhere exhaustive. Indeed, we have yet to see what plants cannot be grown in an IAVs sandgarden.

Plant Spacing

When planting out your sandgarden, we suggest you base your calculations on tomatoes.  They are a high-value crop that is very demanding of nutrients.  In cultural terms, if you can grow tomatoes successfully, you can pretty much grow anything.

Four indeterminate single-stem vine tomato plants may be accommodated in a square metre of iAVs bed.  Use the same spacing for single-stem vining cucumbers and bell peppers.

Cayenne and jalapeño peppers can be spaced 6 to 8 per m2 depending on the variety.

Greens and Brassica species spaced as with high-density or raised-bed gardening – typically 12″ (300mm) in-row x 18″ (450mm) between rows for 6 to 8 /m2.

For backyard purposes, if you use typical spacing for climbing legume crops, you’ll have plenty of space to intercrop lettuce and other leaf crops between rows.

As legumes, beans source their nitrogen from the air, so intercropping with heavy nitrogen feeders like Swiss chard, salad greens and Asian greens makes good sense.

Climbing legumes are generally spaced 6″ to 8″ (150 – 200mm) in-row and 30″ to 36″ (750 – 900mm) between rows

Now, every species (and every cultivar) has its own nutrient and space (and every other kind of) requirement, so our suggestions are merely a guide to system sizing.

Specific spacing and nutrient information are freely available on dozens of gardening websites.  Typically, however, you could anticipate iAVs to yield 130 to 150% more than traditional garden practices.

Nutrient Equivalence

It is very difficult to generalise about the relative nutrient demands of various crops.  When compared to indeterminate tomato – at 4/m2 – the following is a reasonable expectation:

  • Eggplant, melons (trellised) in the range of 60-70% /m2 of the requirement of tomato
  • Cucumber, peppers and Brassica (cole) spp. approximately 40 to 60%  /m2
  • Squashes and gourds (trellised) at 40 – 60% /m2
  • Beans and peas (except for N) approximately 30 to 50% /m2
  • Beets, chard, kale, and spinach, into 20 to 30% range /m2
  • Lettuce (bibb, cos, leaf) in the 10 to 20% range (also dominantly N)   – or less
  • Basil, rosemary, thyme and other culinary herbs ~ 10%
  • Chives, dill, radish – < 5%


Concentrating on seasonal crops will enhance production and since the crops are in their preferred environment, they will be better able to resist infestation and disease.

  • Focus on tropical species in summer months – tomato, pepper, melon, summer squash
  • Spring/Fall crops – beans, greens, herbs, okra, winter squash(es)
  • Winter crops (GH) – snow/sugar peas, Brassica spp., and some greens.

Plant Feeding

Well, there isn’t anything much for us to do, here.

If you feed the fish correctly – and operate your iAVs within the recommended parameters – your plants get fed and watered automatically.

And that’s very fortunate for us because plant nutrition quickly gets complicated once we get into it.

All we need to know is that if we provide quality feed – as a proportion of their body weight based on their stage of growth – we can support a known number of plants.

You’ve heard me refer to iAVs as a living machine.  The fish and plants are the visual evidence of the ‘living’ part of an IAVs…and their state of good health is bears testimony to the state of the microbiology.

The ‘machine’ part of iAVs design…the systematic approach… enables us to adjust the balance between feed rate and production outcomes.

Key Points

  • iAVs produces more clean fresh organic fruit and vegetables – for less water – than any other method.