Eli5: What does it mean to ‘cycle an aquarium’?

Question

Eli5: What does it mean to ‘cycle an aquarium’?

In: 2

Answer 1

‘Cycling an aquarium’ refers to growing a bacterial colony that carry out a nitrogen cycle.

Fish or other animals will produce ammonia as one of their wastes. It’s toxic, but bacteria can break it down into nitrite. Nitrite is still toxic, but another set of bacteria can break it down into nitrate. Nitrate is far less toxic, and can even be used by plants and algae.

Cycling an aquarium involves growing those bacterial colonies so that they’re large enough to process all the waste that the inhabitants of the aquarium produce into at least nitrate. A cycled aquarium is simply one that already has all the bacteria necessary to do so.