Fish, like all other living creatures, produce waste. We can simply flush our waste down the toilet, but fish, what do they do? If you want take good care of your fish, you first have to know a few things about what goes on with their water; in other words, you need to understand the nitrogen cycle. In short, the nitrogen cycle is a complex biological exchange that results in the conversion of toxic ammonia into relatively safe nitrates through a series of chemical steps.

When fish eliminate waste, most of the solids sink down to the bottom of the tank, or get sucked up by the filter. The waste products break down through a biological decay process that produces ammonia as a by-product. Other reasons for the production of ammonia are over feeding and decaying plant material. As more waste products decay, more ammonia is produced. The concentration of ammonia in your fish tank increases continuously. Ammonia is harmful to fish even in small concentrations (.05 to 2 parts per million (ppm)). It burns the fishes gills, causing the fish to slowly and painfully die of suffocation.

So, how do you stop your fish from dying a horribly painful death? Fortunately it’s not so difficult. One way to remove ammonia is through massive weekly water changes, but that isn’t very practical since fish tanks are many times carefully set up in an artful and time consuming manner. Another way to rid your tank of ammonia is to buy chemicals to add to your tank, but this can be costly. The best and most inexpensive way to remove ammonia is to let biology work for you.

In our municipal water supply, there are naturally occuring bacteria called nitrosoma and nitrobacter, called “nitrifying” bacteria. Nitrosoma eats the ammonia and produces a by-product called nitrite. Unfortunately, nitrite is not good for your fish either, but in most cases, a higher concentration of nitrite (about 3-4 ppm) can be tolerated before irreversible damage is done to your fish. You can purchase a nitrite test kit to measure nitrite concentrations from our products page. This is where nitrobacter comes in: Nitrobacter will convert your nitrite to nitrate, which is a relatively safe chemical for your fish.

For most species of fish, a nitrate concentration of 300 ppm is tolerable, which you can measure using a nitrate test kit available on our products page. To keep the nitrate concentration down, use Nitra-zorb, available here at Willa’s Ark, or through weekly water changes. You can go to the Tank Maintenance page to learn how to safely change the water in your tank. It takes about three months for both bacteria to establish themselves in your tank and eat the ammonia your fish produce. The bacteria will grow on all surfaces inside your tank, you can’t see it, but it’s there. It’s that slimy coating you feel on the glass.