Tilapia is the species growers report raising more than any other, and the survey numbers are clear on that much. Love and colleagues asked 257 operations what they raise, and tilapia turned up in 69% of them, with ornamental fish at 43%, catfish at 25% and trout at 10%. That table records what growers stock. It does not record what is easiest to keep alive. The best aquaponics fish for your build is the one that fits your water temperature, your feed budget and your tank, and for a beginner that is tilapia on all three counts.
Feed is the first filter, and it is the one most people skip. Anyone costing out a tilapia aquaponics setup should price a month of pellets first. You buy that bag every week for the whole life of the fish. The protein grade your species needs shapes the running cost far more than the name on the tank ever will, so pick the fish that eats what you can keep buying.
The aquaponics feed protein figures are plain. Tilapia and catfish both grow on feed in the 30% to 40% band, which is the cheap end of the shelf. Bass need 41% to 46%, and you pay for that gap on every bag you carry home. Catfish sitting in the same band as tilapia is one reason they turn up in a quarter of surveyed systems while bass barely register.
Feed is over 50% of variable production costs for most small aquaponics businesses. Work out a month of it at the protein grade your species needs, then decide whether you still want that species.
Water is the second filter, and it is less forgiving than feed. The published operating window is broad by design, and the numbers below are the whole of it. A species either sits inside that band or fights you every week, and heating a tank to suit the wrong fish costs more than the fish is worth.
Those figures describe the system, not one species. Check whatever fish you fancy against the band before you buy. A fish that wants water outside it turns a food build into a heating project, and the power bill never stops. The list is still wider than the survey makes it look. Rainbow trout in low-tech aquaponic systems reached about 1.1 lbs per cubic foot (17 kg per cu m), and growth and flesh quality took no hit at that density.
Tank size settles the rest, and it is the number that first builds get wrong. The recommended small-scale volume is 13 to 53 gallons (50-200 L), and a 13 gallon (50 L) tank supports 50 to 100 small fish. Count that out on paper before the fingerlings arrive. Small fish do not stay small, and a tank stocked by eye is the cheapest mistake to make and the slowest one to undo.
Buy tilapia for the first run and leave bass for a system you already trust. Match the feed grade to the fish instead of grabbing the highest protein bag on the shelf, since 41% to 46% feed poured on a 30% to 40% species is money going straight through the filter. Trout are worth a look once you can hold the water where you want it, since only 10% of surveyed growers raise them and the trial results are good. Stock to the tank you own, not the one you plan to build next spring. The best aquaponics fish is the one you can feed and house without a fight.
Read the full article: Aquaponics: What Works and What It Costs
