An aquarium bioreactor is a specialized device that is used in aquariums to promote the growth of beneficial microorganisms in order to maintain water quality and the overall health of the aquarium environment. Bioreactors can be used in both saltwater and freshwater aquariums, and they can play an important role in managing the nitrogen cycle, reducing the accumulation of harmful compounds, and promoting the growth of beneficial microorganisms.

One of the most common types of bioreactors is the denitrification bioreactor, which is designed to remove nitrate and nitrite from the water. Denitrification bioreactors typically consist of a chamber filled with a substrate, such as bio-balls or ceramic media, on which denitrifying bacteria can grow. The water from the aquarium is pumped into the bioreactor, where the bacteria consume the nitrate and nitrite as a food source, reducing their concentration in the water.

Another type of bioreactor used in aquariums is a bio-pellet reactor, which utilizes bio-pellets, a medium to house beneficial bacteria cultures that convert fish waste, urine and uneaten food, into less harmful substances. The reactor provides an oxygen-rich environment where the bacteria can multiply and thrive, breaking down organic compounds and reduce the buildup of harmful chemicals.

Both types of bioreactors can help to maintain the overall health of the aquarium environment by providing a natural way to reduce the build-up of harmful compounds and promoting the growth of beneficial microorganisms. They can be a valuable tool for aquarium hobbyists and professionals who want to keep their aquarium water clean and healthy for the inhabitants.