Tank culture offers an alternative to traditional pond aquaculture and can be used in indoor facilities such as unused barns or other buildings. Tank culture systems are examples of recirculating aquaculture systems (RAS). For example, equipment or structures already in place in a former hog operation can be converted for use as a RAS. By retrofitting equipment and reusing water, a RAS can be developed to produce fish in a cost-effective manner. The conversion can require a significant investment, however, so before beginning it is important to gather as much research-based information as possible and to learn about fish culture, water quality, marketing, and other aspects of aquaculture.