The present invention provides an aquaculture system in which a biofloc technology is introduced so as make it possible to easily control water quality (C/N ratio) of culture water. Provided is a biofloc technology-based aquaculture system in which a culture water tank is provided with a nitrifying bacterium-immobilized material in which nitrifying bacteria are supported on a carrier. It is preferable that a water-permeable container filled with the nitrifying bacterium-immobilized material is disposed downstream of an air injector and/or an aeration apparatus.
