Once you have your aquaponic system set up and your test kit in hand all you need to do to start the cycling process is add a source of ammonia. Traditionally this has been by adding fish and using the ammonia from their waste, but we’re not a big fan of using fish as an ammonia source. Without nitrifying bacteria established in the system, the rising ammonia and nitrite levels may exceed toxic levels for your fish. Instead, we prefer a technique called “Fishless Cycling” where an external source of ammonia is added to your aquaponics system to establish nitrifying bacteria before your fish arrive in the tank. Why is this?
First, both you and your fish will likely experience much less stress because you will not be worrying about your fish health through the nitrifying process. Second, you can more precisely control how much ammonia is added to your system during cycling. For example, if you see that your ammonia level is creeping up to 8 ppm, but no nitrites have shown up yet, just stop adding ammonia for a few days and let the bacteria catch up. You can’t do this with fish, as 8ppm of ammonia will surely kill them!
The practical result is that with Fishless Cycling you can fully stock your tank once cycling is complete, versus gradually increasing your stocking levels as is recommended when cycling with fish. This is especially beneficial to those who are growing aggressive or carnivorous fish because they are less likely to attack each other if they are all introduced to the tank at the same time.