In the natural environment, large bodies of water provide the cleansing action necessary to disperse the waste substances produced by fish. In the closed confines of an aquarium, fish depend on the person who sets up the aquarium to provide an efficient system to purify water.
Biological filtration is a natural means of removing toxic ammonia based wastes from the aquarium.
The establishment of a well-balanced Nitrogen cycle is paramount for the health and success of any aquarium.