Biofloc technology (BFT) is a fish farming system which recycles waste nutrients as fish food. Biofloc, specifically cultured microorganisms, are introduced into the water to form microbial protein from toxic fish waste and other organic matter in the water. This helps maintain water quality as well as lowering costs. Candidate species must be resistant to environmental changes, be able to tolerate high stocking density, adapt to changes in dissolved oxygen, and be able to take microbial protein as food. BFT is currently used in large-scale shrimp and finfish farms, mainly in Asia.