Frequently Asked Questions

Background

Is Sandponics and iAVs the same thing?

 

Yes.  Integrated aqua-vegeculture system, iAVs and Sandponics are all the same thing.   The full name is quite a mouthful, and even iAVs has no meaning for those who are unfamiliar with the method, so we decided to use Sandponics as iAVs’ street name.  Many people already know aquaponics, so we rationalised that connecting to the ‘ponics’ might be helpful while using the ‘sand‘ to describe the principal difference between iAVs and all of its descendants.

How does Sandponics differ from Aquaponics?

The three principal variants on the aquaponics theme are (in chronological order)  sandponics, flood and drain and deep water culture. Sandponics utilises sand as the growing media.  Flood and drain aquaponics uses gravel, clay pebbles or other coarse media.  Deep water culture (DWC) – also known as raft culture – has no media as such.  The plants are supported by the rafts with their roots in direct contact with the water.

Sand

How can I determine if a particular sand will drain effectively without knowing the particle size range?

You build a simple sand test rig to establish its hydraulic conductivity…or the rate at which water passes through the sand.  You can learn more about the sand test rig and how it works…HERE.

Building an iAVs

How do I size an iAVs?
What can I expect to be able to grow in my proposed backyard iAVs?

iAVs has the capacity to produce fish and fresh vegetables sufficient to provide a family with 200 kg of fish and 1,400 kg of vegetables (fruit) per year in a footprint equal to an automobile parking space. *

More detail to be found in this article.

*Assumes a sub-tropical or temperate climate or controlled environment that will permit year-round plant production.

Plants

What plants can be grown in an iAVs?

 

The better question (and the much shorter list) is…”What plants cannot be grown in an iAVs?”

How many plants can I fit in each square metre of iAVs sand bed?

Various plant spacings are provided in Sizing an iAVS.

What bio-chemical role do the plants play in an iAVS?

 

As long as there are sufficient plants in an iAVs, the pH remains stable at around pH 6.0 to 6.4

When the researchers operated the systems without plants actively growing in the ‘sand-bed’ (biofilter) to act as a living (active) buffer and nutrient sink, the pH of the water rapidly dropped to levels dangerous to fish survival while ammonia and nitrite concentrations increased to toxic levels.

Water

How much water does iAVs use?

Including annualized losses for evapotranspiration and incorporation into biomass (food) at 85% of total input and a seepage loss of 6%, each liter of water utilized by the IAVS technique can produce 6 g FW of fish and 17 g DW of vegetables. Collectively, tilapia and tomato yields result in 0.7 g DW of protein and 7 Cal. (or 7,000 calories) per liter of water used.

Irrigation Regime

How does the iAVs irrigation regime work?

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.  Assuming 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:

  • 6:00am (dawn or pre-dawn) – 1st pump cycle of the day starts)
  • 6:30am – drainage completed.  Feed fish all they’ll eat in 15 minutes
  • 8:00am – 2nd pump cycle (1/4 of tank volume, each)
  • 10:00am – 3rd pump cycle
  • 12:00pm – 4th pump cycle
  • 1:00pm – Feed fish all they’ll eat in 15 minutes
  • 2:00pm – 5th pump cycle
  • 4:00pm – 6th pump cycle
  • 6:00pm – 7th pump cycle
  • 8:00pm – 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 of the suspended solids (including the fraction too small to see).

Research Trials

Where can I see photos of the Ratio trials?
Where can I learn more about the Ratio Trials?