The Nitrogen Cycle in new setup aquarium.

“Cycling the aquarium” is the first step, after buying all the equipment, to start up a new aquarium. Without the nitrogen cycle, the aquarium is not a safe place for fish and it understanding is a key to healthy tropical fish. As your tropical aquarium is such “small world” all toxins (especially ammonia) generated from rotten food, feces and urine from fish and also dead plants may become deadly in matter of hours. Fortunately, certain types of bacteria (Nirosomonas) can break down ammonia into a less toxic substance called Nitrite (NO2-). After a few days Nirosomonas bacteria start to grow in your tank (particularly in filter and gravel) and drop ammonia levels to zero. The Nitrite is less toxic than ammonia, but still can kill your fish. As next step another type of bacteria Nitrobacter starts to grow. The Nitrobacter breaks down Nitrite (NO2-) and turns it into Nitrate (NO3+). The Nitrate is only toxic in really high levels which you can control by regular partial water changes. The Nitrate is used by aquatic plants as a fertiliser. It takes about 4-6 weeks for the aquarium to balance and be able to reduce all of the waste material (ammonia) to a less toxic substance (Nitrate).  

It takes about 4-6 weeks for the aquarium to balance and be able to reduce all of the waste material (ammonia) to a less toxic substance (Nitrate).

By adding outside bacteria you can speed up the process and often significantly decreasing the overall cycle time. Seeding the tank can reduce the overall nitrogen cycling time to as little as a few days. As source of the nitryfying bacteria you can use filtering material from an established tank or substrate. You can also buy commercial products with bacteria in liquid.