Aquaculture is one of the fastest growing food production sectors globally. Due to continuous growth, ecologically, economically and socially sustainable sites for aquaculture are already in use, which has caused a need for new fish farming techniques. Recirculating aquaculture systems, technology that recycles and saves water, has expanded in recent years. The technology has not yet achieved economic viability, mainly due to high investment and operating costs. In addition, the operation and management of bioreactors has been one of the biggest issues, which microbiological processes were studied by M.Sc. Jani Pulkkinen in his dissertation.