The iAVs Promise

The iAVs Promise

OK…we’ve talked about what Sandgardening is and what a sandgarden looks like…and how it works.

We’ve shown you that it’s easy to build and simple to operate…and that it’s productive, resilient and sustainable.  And we’ve said that not only will it save you money, but it can earn you money, too.

Sandgardening can do lots of things…some amazing things…but when it comes to what goes on your table, we encourage you to be sceptical.  

Rather than expect you to take things at face value, this is where we quantify things …where we stop talking in glowing terms and start putting up the evidence to support our claims.

Clean fresh organic food

Because they are toxic to fish, sandgardening uses no chemical fertilisers…or synthetic herbicides or pesticides. The fish that we grow yourselves only have in them what we provide …and that’s the way we want it when it comes to our personal food chain.

If something grows outside your back door and you get to eat it within minutes of harvest – you will never view ‘fresh’ claims from supermarkets in quite the same way again.

Ease of construction

A sandgarden is little more than two containments – one for the sand and the other for the water.  These containments can be fabricated from a variety of materials, recycled materials and, in its simplest iteration, it may even consist of lined holes in the ground.

Ease of operation

The ongoing operation of a sandgarden is little more than checking water levels, feeding fish, planting seeds/seedlings, culturing plants and harvesting.  The workload is associated with a Sandgarden is much less than that of a traditional garden.


Sandgardens are scalable from tiny desktop demonstration units…to backyard/village gardens …to commercial cropping spaces of more than 1,000 square metres in area.  

Any question of commercial scalability was resolved by 1994, when two men Boone Mora and Tim Garrett (neither of whom had a background in horticulture) received a United States Department of Agriculture grant to trial iAVs on a commercial scale.  

To provide a brief background, Mora was a retired veterinary surgeon and Garrett was an extension officer with a local environmental resource management NGO – neither of them had any formal training or experience in aquaculture or horticulture.

They built a 10,000 square foot greenhouse…and two 26,000-gallon fish tanks (for a total of 52,000 gallons (just under 200,000 litres) and about 52,000 gallons of sand under horticultural management.

Long story short, they knocked Mark McMurtry’s numbers out of the park…almost doubling his production of both fruit/vegetables and fish.


In simple terms, productivity is a way to measure efficiency.  Efficiency is about maximising outputs while minimising inputs.

In productivity terms, iAVs is about getting MORE – for LESS.

More food…for less water…less energy…less space…less risk!

MORE food for LESS space

Food Production

  • Yields attained in Raleigh, NC indicated that a human-powered sandgarden – equal in size to that of a car parking space – could produce 150kg of fish and 1,100kg of vegetables per year…for an average of 3 kg (7 lb) fish and 21 kg (46 lb) vegetables each week.
  • Taking an ‘appropriate technology’ approach to the same space and the production increased to 200 kg of fish and 1,400 kg of vegetables (fruit) per year…and beyond.
  • Each 1.0 kg of fish weight gain provided enough of all the required plant nutrients to sustain 2 tomato plants yielding 5-7 kg of fruit per plant over 3 months.
  • Tomato yields exceeded 6.8 kg (15 lb) per plant.

MORE food for LESS water

Water Use

  • Sandgardening can achieve 120 to over 300 crop applications with each unit volume of water…subject to the crop and season.
  • The rate of water input (replacement of evapotranspiration losses) in the IAVS technique ranges from 1 to 3% of system capacity per day.
  • The IAVS technique requires only 11 cubic meters of water per year for each 1.0 cubic meter of system capacity (at a 3% per day rate of loss).
  • Each litre of water employed can produce, in fish and fruit, 0.7 grams of protein,7 kilo-calories food-energy – and most essential vitamins.
  • Including annualized losses for evapotranspiration and incorporation into biomass (food) at 95% of total input and a seepage loss of 5%, each litre of water utilized by the Sandgardening technique can produce 6 g FW of fish and 17 g DW of vegetables.

MORE food for LESS energy

Energy Use

While the water use efficiency of Sandgardening is exciting news for those people who live in arid or water-stressed places, it’s efficiency in the way it uses energy is no less impressive.

The sum of the water pumping intervals in the technique developed at NCSU is less than 2 hours per day. The energy demand of this technique is approximately one-twelfth that of other recirculating aquaculture/hydroponics techniques.

A sandgarden capable of feeding a family of four can be operated manually – no need for grid or solar power.

Solar power is viable for commercial sandgardens in areas where mains power is unavailable or unreliable.

TWO crops for ONE drop…a crop of fish for the same amount of water 

that it would otherwise take to just grow the fruit and vegetables.

Fish and Fish Feed

Fish feed is the biggest expense associated with most sandgardens so it follows that the more food we can produce for a given quantity of fish food, the better.

  • Each kilogram of feed input to the system will result in the production of approximately 0.75 kg of fish and 6.70 kg of fresh vegetables.
  • Fish yields ranged from 50 to 70 kg per cubic meter of water per year (0.41 to 0.57 lb/gal/yr).
  • Feed conversion ratios for fish of average market size (0.25 kg) ranged from 1:1.1 to 1: 1.3.


One of the biggest bugbears with conventional gardening methods is the amount of supplementation that’s required.  Organic soil requires large quantities of compost each crop cycle – and then it will require a fertiliser of some sort…then foliar sprays.  If the soil is deficient in some nutrient or the other, they will need to be added, too.

iAVs Sandgardening requires nothing more than the fish be fed a reasonable quality fish food.  Everything the plants need will follow from the simple act of feeding this ration to the fish.

The Best is Yet to Come

Because of the unique circumstances of its evolution, iAVs has never been optimised.  

The research trials sought to achieve two goals…to prove the concept (the Proto ’86 trial)…and to establish the relationship between the fish tank and sand biofilter volumes (the Ratio 411 Trials).  

These metrics are simply the outcome of those trials…and provide a performance baseline.  

The production outcomes were exceeded by Boone Mora and Tim Garrett in the USDA-funded Commercial iAVs Trial…and it’s reasonable to expect that they will be exceeded by other operators as more is learned about the method.


Resilience refers to the ability of a food production method to withstand catastrophic failure due to equipment breakdown or disruption to the power supply. 

The living organisms in integrated aquaculture systems of most types will begin to suffer within minutes of the water ceasing to recirculate.  For that reason, they pump water continuously.

With a sandgarden, however, the combination of the particle size range of the sand and the intermittent irrigation regime means that the sand drains well – while retaining sufficient moisture to sustain the plants between irrigation events.

The mechanical and biological filtration afforded by the sand – enables the system to rest – for up to 10 hours overnight without putting it at risk.

A sandgarden doesn’t prevent you from suffering equipment failure or power interruptions, but it is designed to give you sufficient time to discover – and respond to – such events.

It’s natural resilience…coupled with sound farming practice…offers cost-effective risk management.


Sustainability is about the capacity for the Earth’s biosphere and human civilisation to co-exist.

Mark McMurtry designed the iAVs with the idea that it should enable “impoverished villagers to source their nutrition without harming the planet.”

While the capacity to produce more food for less water is arguably its most important concession to sustainability, other Earth-friendly features include:

  • More for less energy.  Human-powered options available.
  • No waste stream of any kind.
  • No chemical fertilisers or synthetic herbicides or pesticides.
  • Low embedded energy in construction materials.
  • Cost Effectiveness

Overwhelmingly, people think of conventional gardening as work that must be done…and money that must be spent.  Often, these folk garden for the pleasure that growing plants gives them…and the expense of that is just part of the deal.

While clean fresh organic food is usually their main objective, the best gardeners may even save money…but most will not.

The idea of a cost-effective gardening method that works for us may take a bit of getting used to initially (accustomed as we are to having to do the work) but it is well within the scope of a Sandgarden.

If a system cost little to build and produces more food for less water and energy – without the need to buy fertiliser, herbicides and pesticides…or to supplement the system…then it may be assumed to be cost-effective.

To summarise…Sandgardening is simple to understand…easy to build and operate…and productive, resilient and sustainable.

And not only will it save you money, but it can also actually make you money.

What’s more, we still don’t know what the upper limits on all of that productivity, resilience and sustainability.

Well, that’s it!  

Now, you know what Sandgardening is…how it works…and what it can do for you.

You know that the claims that we make are in fact, backed up by research data and the experience of our growing community of commercial farmers and domestic sandgardeners.

iAVs Sandgardening provides several performance benchmarks…and a clear invitation to exceed them.

What we do know is that the numbers arising from the research trials and the USDA commercial trial are merely a baseline…so it’s what we have yet to learn about Sandgardening that is our focus moving forward.