7 – Operate


If you’ve reached this point, please accept our heartiest congratulations.

You just became a sandgardener – with skin in the game

If you’re following our lead, your new system has been running for a couple of days.

One of the core goals of the iAVs irrigation regime is to remove not less than 25% of the fish tank volume during each 15 – 20-minute pumping cycle.   In effect, we turn over the entire tank volume twice per day.

Assuming the correct tank design (sloping/cone-shaped bottom) and pump capacity, all solids will be removed during each pumping cycle and the water will be crystal clear.

For example:

  • 6:00 am (dawn or pre-dawn) – 1st pump cycle of the day starts
  • 6:30 am – drainage completed.  Feed fish all they’ll eat in 15 minutes
  • 8:00 am – 2nd pump cycle (1/4 of tank volume, each)
  • 10:00 am – 3rd pump cycle
  • 12:00 pm – 4th pump cycle
  • 1:45 pm – Feed fish all they’ll eat in 15 minutes
  • 2:00 pm – 5th pump cycle
  • 4:00 pm – 6th pump cycle
  • 6:00 pm – 7th pump cycle
  • 8:00 pm – 8th pump cycle (dusk or slightly after, depending on season and location).

Note: Pump remains OFF overnight.

If you provide these 8 pump cycles of 1/4 tank volume each per day, then you’ll have 2 complete tank exchanges daily and a full tank volume filtration following every feeding.  

If you do this then solids will NOT accumulate nor reduce dissolved oxygen levels nor stimulate alga growth or disease organisms.  

The ENTIRE point of filtration (e.g. sand) is the removal of the fish waste from the water column.  

The first goal is to extract the ‘wastes’, then let the sand filter out ALL the suspended solids (including the fraction too small to see).

If the prescribed irrigation feeding and irrigation regimes are followed…and the system uses tilapia, carp or similarly robust fish species…overnight irrigation of the sand beds is not needed.  It also saves energy and provides a protracted opportunity for the sand beds to drain while still retaining sufficient moisture to sustain the plants.

It may be applicable to other fish species, too…but that has yet to be confirmed.

Operating Checks

You can check on your new sandgarden as often as you like…but not less than daily.

Ensure that:

  • The fish and plants both appear normal in their behaviour and condition.
  • There are no leaks or equipment failures
  • the water pump is operating correctly
  • the irrigation events are happening with the specified frequency
  • the timer is set at the correct time
  • the plants are free of insect infestation or disease
  • the water tank is topped up with clean water adjusted to pH 6.4.
  • The correct measure of fish feed is given to the fish.

From this point on – for as long as you want – your plants will continue to grow – with little more than daily monitoring…and periodic planting and harvesting.

Now that you’re up and going, it’s useful to take stock of what’s happened so far.

Taking Stock

Before we begin to enhance its performance, let’s take stock of our Starter system, so far.  

We now have a 1000-litre fish and a 2000-litre sand biofilter with a growing area of six square metres.  The sand bed is filled with clean, inert sand that drains well.

We’ve added a hundred 15g fingerlings…so we’re starting the daily ration off at around 50 grams. With two feeding times, that means 25 grams per feed. Give the fish the initial 25g and, once they’ve eaten that, offer them small additional amounts until their interest slows down. 

Weigh what feed is left and deduct that from the measure that you began with – to arrive at a nominal daily ration. Each ensuing day, feed the total amount provided the day before….as the base amount and then in the ensuing minutes, offer them some more….and the total that is fed that day becomes the new base daily rate….and so on.

Doing this on a daily basis will quickly get you in tune with the very direct relationship between what your fish are eating and what you can grow. This is a skill that develops over time. There’s a lot that can be said about feeding fish, but this is all you need to know at this stage. It’s simple and easy….and effective!

Ideally, the last feed should take place at around 2:00 pm.  This ensures that solid wastes are removed from the fish tank prior to the system shutting down for the night.

The sand bed has been planted out to a mixture of greens, legumes and fruiting crops (at least 50%).  They should have plenty of light – more is better.

At two-hourly intervals (during the daylight hours), the pump moves approximately 250 litres of solids-laden water to the sand beds.  Eight such events will turn over the fish tank’s contents twice in every 24-hour day.

The water in the system has been adjusted to a pH of 6.4.  Rainwater is best.

Since we are using warm water fish species, the temperature in the fish tank is maintained within the range of 24oC – 30oC.

When the pump stops, the bed drains until the next irrigation event.  The water pump remains off overnight.

The air pump operates continuously – ensuring adequate dissolved oxygen for the fish, the plants and the microbial life that drives the system.

And as long as you top up the water, feed the fish and plant seedlings and harvest the grown plants, your new system will provide you with some delightful French radishes in less than three weeks, quickly followed by your first leafy salad greens and soft herbs (like coriander/cilantro) followed a couple of weeks later by an expanding feast of Asian and salad greens.

Just your system starts to evidence something of its true potential at around 100 days, the daily harvest will include increasing quantities of tomatoes, cucumber, peppers, and beans as the unit ratchets up to grow the nutrient-dense ‘thick and hearty’ foods for which it is best known.

Eventually, word of your prowess with a sandgarden will begin to leak out – and you’ll find increasing demand for your clean fresh organic food – first from your mother – then other family and friends – and then paying customers.

It’s time to expand your iAVs Sandgarden.

Expanding your iAVs Sandgarden 

Whether it be the desire for more food (for a family perhaps) or a greater variety of plants, your mind will eventually turn to expansion.

Your simplest option is to set up another Starter iAVs system…and then add another one.

As you get your head around working with iAVs, you can expand the number of such units to four. This allows you to do side-by-side comparisons of fish species, plant cultivars, and operating parameters – a very useful thing indeed. It will also provide all the freshwater fish and fruit and vegetables you’ll need for a family of four…with teenage (hollow-legged) children.

If you continue to extend your system, this way, you will end up with 16 such units…and your own research facility…and you will quickly establish yourself as the iAVs expert in your area. 

At that point, you will be harvesting fish on a weekly basis. Not only will you be drawing income on a weekly basis, but you will also be able to expand your operation to become an iAVs demonstration centre…where you can even entertain fee-paying students.

Before we reach that point, however, we need to know what your iAVs goals look like. Are you just looking to grow food for your family? Or do you want to sell food to your local market? Or do you want to do that…and run a training business, too?

Regardless of your aspirations, I recommend the modular approach because it allows you to grow commensurate with your knowledge and skills. It also allows you to build your operation over time, using the production income from each unit to fund those that follow. 

The sizing of the Starter Kit sandgarden is no accident.

One Starter Kit sandgarden will feed one person.

Four such sandgardens become a Family Kit…24 square meters…able to feed a family of four.

Four Family sandgardens, become your own small farming research unit…able to undertake useful comparative research – 96 square metres – and function as a local iAVs Demonstration and Interpretation Center – able to train local gardeners and farmers in the iAVs method. 

And it all starts with a single Starter iAVs.

Now, if you can’t think of ways to generate income with a 16-unit iAVs Sandgarden, you are lacking imagination. And you may have reasons to go beyond this…to where you have several such 96-square-meter small commercial learning and development modules.

There comes a point where you are unable to personally manage the daily workload that comes from an expanding installation. At the point where you need to hire labour, your first consideration should be how that will impact your life – and we should acknowledge that the most efficient area on your farm is that which meets your needs and reasonable expectations…that you operate with no other labour than your own.

Now, you may be thinking well ahead of that bootstrapper’s approach to growing an iAVs Sandgarden. You may have visions of acres of Venlo-style controlled environment cropping greenhouses – with little robots zipping around to do all the actual work. 

If that’s the case, you’re still in the right place – but just the wrong department. Let us know when you’re ready to talk about commercial iAVs, and we’ll direct you accordingly.