While this may be old hat, I really believe that the nitrogen cycle cannot be over-emphasized in terms of its importance for successful aquariums. With new aquarium hobbyists, it is absolutely critical that they understand the nitrogen cycle. To cover it quickly, the nitrogen cycle is the key to all life in an aquarium. Fish, decaying food, plants, etc., all produce ammonia, which is toxic to fish. Established bacteria convert ammonia to nitrite, which is slightly less toxic. A second group of bacteria then convert nitrite to nitrate, which is much less toxic than either ammonia or nitrite.
Nitrate is removed from the fish tank by live plants, water changes and/or providing an anaerobic environment for a third group of bacteria to live, which convert nitrate into harmless nitrogen gas.
It has been said that success at keeping a fish tank really gets down to success at keeping bacteria – the beneficial bacteria of the nitrogen cycle. This is absolutely true and should be stressed often. Some aquarists say that they don’t have time for all that “scientific stuff.” Well, it’s not really that technical, and it is very important. Rick Preuss of Preuss Animal House in Michigan simplifies the nitrogen cycle by talking about “storms” developing in a new fish tank. The first storm is an ammonia storm, and then the nitrite storm and finally the nitrate storm. This is a helpful way to think of the nitrogen cycle.
As a retailer, you can dramatically reduce the problems that aquarium hobbyists, especially first-timers, have with the nitrogen cycle by passing out an information sheet that explains it. You also can help them out by giving or selling them filter material that has been “charged” with live bacteria, or selling them any of the excellent live bacteria products on the market today. Whatever you do, if you do not get aquarium hobbyists to understand the nitrogen cycle, they will never be successful keeping fish and one more tank will end up in a garage sale, with the seller saying, “Fish are too hard to keep.”