The grow beds attached to the fish tanks have a variety of plants which are as follows:
small system - 750l fish tank - 2 x 250l grow beds - galangal , tumeric and nasturtium
medium system - 1250l fish tank - 4 x 250l grow beds - strawberries, fennel, tomato, cabbage, lettuce, warrigal greens, chives and water cress
large system - 2500l fish tank - 2 x 1000l (approx) grow beds - kale, flat leaf parsley, parsley, warrigal greens, thyme, chicoria, and spring onions
The systems require very little work - each day I feed the fish a handful or so of Barramundi pellets and check that the aerators and pumps are working.
This only takes a couple of minutes at most. I rarely check the water chemistry any more as it doesn't seem to change much. The plants seem to be growing well enough, and I am understocked as well, giving me a fair amount of leeway.
The basic biology behind aquaponics is fairly simple: the fish waste product is ammonia, every 30mins ( actually 1 system uses a continous pump) a pump is activated (via a timer) and some water is pumped into the grow beds. In the gravel of the grow beds, bacteria convert the ammonia first to nitrite and then nitrate. When the water level almost reaches the top of the gravel the pumps turn off, and the water syphons back into the fish tank. In other words, it is a closed loop with bacteria converting ammonia to nitrate. Now nitrate is relatively non toxic to fish, and is of course an excellent plant food.
In the gravel plants that use nitrate can be planted - these are especially leafy greens such as spinach, lettuce etc. As can be seen from the lists above though there are lots of plants that can be used. My only concern about growing food plants like this is really how nutritious they are - the brix readings seem to be on the low side. However it is a really simple way to grow fish to eat once it is set up. It provides us with 1 fish/week and some to give away to family and friends.
The idea of the 3 systems was - small tank for fingerlings, medium tank for 1 year old fish and large tank for 2 year old fish. As Jade Perch are of plate size in about 12months however, when I restock in November with fingerlings from the hatchery, I am going to try a different species in the middle sized tank - not sure which type yet.
Jade perch have been really easy to farm and have been a good starter species. They are also very high in omega 3 fatty acids - better than salmon and tuna apparently.
Murray Hallam's web site is an excellent source of information on Aquaponics -if you are interested in this topic he is very approachable and more than willing to share his knowledge and give advice.
http://www.aquaponics.net.au/aqua1/
Tom
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