Biofloc Technology
Biofloc technology (BFT) is an alternative fish farming system where recycling and reuse of waste nutrients as fish food is employed. The principal approach of BFT is to culture suitable microorganisms along with aquatic species (fish or shellfish) to produce a sustainable system, benefited by the minimum or zero water exchange. The technology works on two main background: History of BFT. The first BFT was developed in 1970s at Ifremer-COP (French Research Institute for Exploitation of the Sea, Oceanic Center of Pacific) with "Penaeus monodon", "Fenneropenaeus merguiensis", "Litopenaeus vannamei" and "L. stylirostris"... Israel and USA (Waddell Mariculture  Center) also started Research and Development with Tilapia and "L. vannamei", respectively in the late1980s and 1990s. Now this technology successfully runed in TNBIOFLOC Mayiladuthurai, tamilnadu. TNBIOFLOC foundar name is Mr.Gajendraprabhu since 2017. Commercial application started at a farm in Tahiti (French Polynesia) in 1988 using 1000m concrete tanks with limited water exchange achieving a record of 20–25 ton/ha/year in 2 crops. A farm located at Belize, Central America also produced around 11-26 ton/ha/cycle using 1.6 ha poly lined ponds. Another farm located in Maryland, USA also produced 45 ton shrimp per year  using ~570 m indoor greenhouse BFT race-ways. BFT have being successfully practised in large-scale shrimp and finfish farms in Asia, Latin and Central America, USA, South Korea, Brazil, Italy, China, India and others. However, research on BFT by Universities and Research Centers are refining BFT, for farm application in grow-out culture, feeding technology, reproduction, microbiology, biotechnology and economics. The role of microorganisms. Microorganisms play the vital role in feeding and maintaining the overall health of the cultured animals. The flocs of bacteria (biofloc) is a nutrient rich (protein-lipid source) available as fish food throughout the day . The water column shows a complex interaction between living microbes, planktons, organic matter, substrates and grazers, such as rotifers, ciliates, protozoa and copepods which serves as secondary source of food. The combination of this particulate matters keeps the recycling of nutrients and maintaining the water quality The consumption of floc by the cultured organisms has proven to increase the immunity and growth rate, decrease feed conversion ratio and reduce the overall cost of production. The growth promotional factors has been attributed to both bacterial and plankton, where up to 30% of the total food is compensated in shrimp Species compatibility . There is a norm of species compatibility for culturing in BFT. To achieve a better growth performance, the candidate species must have the resistance to high stocking density, adapt to changes in dissolved oxygen (3-6 mg/L), settling solids (10 --15 mL/L) and total ammonia compounds, omnivorous habits or ability to take microbial protein as food.