Nitrogen Cycle
Stage 1: Ammonia (Harmful)
The nitrogen cycle begins with waste from poop, pee, rotting food or plants. These all give off ammonia as they breakdown. Ammonia will continue to build up in your tank, reaching deadly levels, until a beneficial bacteria forms. These bacteria naturally appear in your tank on their own and once they grow in number, they can eat ammonia as quickly as it appears. You know these bacteria are present in your aquarium when your ammonia levels begin to decline, typically after the first week. When that happens, the second stage of the nitrogen cycle begins
Stage 2: Nitrites (Harmful)
As your ammonia levels begin to decline, the nitrite levels begin to rise. This is because the bacteria that eat the ammonia give off a new chemical – nitrite. Just like ammonia, nitrites are highly toxic to your fish.
As nitrite levels rise, a second bacteria appears in your aquarium. Once this bacteria grows in number, it can eat nitrites as quickly as they are produced. You know this bacteria is present in your aquarium when you see your nitrite levels begin to fall. When this happens, the third and final stage of the nitrogen cycle begins.
Stage 3: Nitrates (Harmless)
As your nitrite levels decline, the nitrate levels rise because the bacteria that eat nitrites give off a new chemical – nitrate. Nitrates are the final product of the nitrogen cycle, and are relatively harmless to your aquarium, in small amounts. As nitrates build up, they can become toxic to your fish. Nitrates can be lowered back to harmless levels by performing a water change. This is one of the reasons why you should be performing regular water changes on your aquarium.