What is Aquarium cycle?

Cycling is the process of establishing a population of living bacteria within an aquarium. Housed on the filter media, substrate, and surfaces inside the aquarium, bacteria biologically filter the water as they carry out their normal life functions. Collectively referred to as a biofilter, the bacterial colonies should be well-established before introducing animals into the aquarium, or survival is unlikely. This can take several months or even years for certain conditions to develop if you are prepared for initial failure after adding fish or plants. Most tropical fish will tolerate just about any ammonia level provided there is adequate room for plant growth before it reaches potentially dangerous levels.