The rise of the homo sapiens thousands of years ago, transformed the planet forever. Humans due to their superior intellect, communication and organization have always harvested the nature to its maximum which was essential for rapid human growth, industrialization and modernization. This ever growing human population globally has severely depleted the natural resources like land, oil, minerals, air quality, water, food etc. After the industrial era, backyard and small scale animal rearing was transformed and commercialized into organized large scale animal husbandry industry, to sustain the ever growing food demands. Scientific aquaculture, than traditional methods can be a sustainable food source for the humans in the future, eliminating the malnutrition and also strengthening the economy. Aquaculture production which was 40 million tonnes in 2008 is projected to rise to 82 million tonnes in 2050 (FAO, 2010). India stands second in culture fisheries globally and the industry grew six times in last two decades. This freshwater fish farming increased by whooping 80 % than during 1980”s, with current annual yield around 3 t ha-1 (DADF, 2017). Current focus is on making the aquaculture industry more efficient, profitable, environment friendly, maximising production/yield which will reduce the cost of production and the depletion of natural resources. Another perspective is production of healthy, nutritive, antibiotic and hormone free high quality protein feed for national and international markets according to Hazard Analysis at Critical Control Points norms (HACCP).
The recent necessity driven technological advancement in the aquaculture industry has lead to development of new improved species, specialized small tanks where the microenvironment is regulated, nutritive fish feed and waste management with the help of microorganisms and chemical agents which enhanced both the production and economic returns. Biofloc technology (BFT), an eco friendly technique where a culture of microorganisms is used for efficient utilization of feed, improves water quality and allows reutilization of feed and natural wastes has brought revolution in small and large aquaculture enterprises. Biofloc systems were developed to improve the production cost, where cost of feed, availability of land and water, waste management were major limiting factors. Biofloc forms a protein rich live food due to conversion of unused feed and waste recycling, in particular nitrogen and is mainly composed of microorganisms, bacteria, fungi, algae, invertebrates etc (Kuhn et al., 2010). The floc size can be 50 to 200 microns consisting of loose matrix of protein rich live feed made up of mucus secreted by bacteria’s and bound by filamentous microorganisms. The major metabolic waste produced by aquatic animals is ammonia which is highly toxic and has to be removed periodically. This accumulation of ammonia and other nitrogenous wastes hamper the normal growth and reproduction and are fatal to the cultured animals. Biofloc technique ensures growth of Heterotrophic organisms by changing the carbon : nitrogen ratio, so that the bacteria can assimilate the waste ammonium for new biomass production, thereby reducing the ammonium toxicity and need to change the water regularly.
Biofloc as nutritious high value food and waste management
In the intensive culture systems more than 50 % of production cost is for feed. However the cultured animals are not able to fully utilize this commercial feed leading to wastage and suboptimal growth rates. The Biofloc enhances the feeding behavior of the animals as it mimics the natural feeding conditions. The composition of Biofloc can be variable due to differences in the culture conditions and stage of floc maturity. The protein content varies between 20-50 %, fat ranges from 0.5 to 41 %, carbohydrate 14-59 % and fibre 5-7 %. It is also good source of minerals and vitamins like phosphorus etc. Free amino acids like alanine, glutamate, arginine and glycine etc, are also produced naturally. Bioflocs also contain various bioactive compounds like, essential fatty acids, carotenoids, free amino acids and chlorophylls (Ju et al., 2008), trace minerals (Tacon et al., 2002) and vitamin C (Crab et al., 2012). Bioflocs may also contribute to the supply of essential nutrients and digestive enzymes either through the stimulation of endogenous production or microbial secretions thus acting as probiotics.
The working of Biofloc depends on symbiosis and commensalism of different type of bacteria’s (heterophilic & others), microalgae, protozoa’s, fungi, zooplankton, nematodes etc. Initially during the formation phase a high nitrogen : carbon ration of 12–20:1 is essential to establish the heteroplilic bacteria which use the organic matter, after that carbon : nitrogen ratio of 6:1 is maintained for optimum working of the Biofloc. This biomass works together, utilizing intermediary metabolic as well as end metabolic products for their growth and reproductive purposes. The dynamic Biofloc system constantly supplies energy, micronutrients, microbial products and antioxidants to the cultured animals, acting as immune-stimulating agents and growth promoters, while reducing feed cost. This leads to maximum feed conversion efficiency, increases natural resistance to various infections and pathogens, exponentially increasing the growth/production cycle in culture animals. Probiotics can be also added to the Biofloc, during the initial phases which help to establish a healthy Biofloc, to maximize feed, waste, intermediary metabolic product utilization. Because of all these advantages the BFT is used for rearing numerous shrimp and fish species, both in developing/nursery and finishing stages very successfully.
Biofloc for efficient water maintenance and utilization
Water quality and quantity both affect the growth and production cycle in cultured animals. It has been reported that by using BFT technology, 40-70 % less water is utilized. Due to addition of feed, normal metabolism, excreta; temperature, dissolved oxygen (DO), pH, salinity, solids, alkalinity, and orthophosphate vary constantly. These variants form the microenvironment and are to be maintained at optimum conditions. Changes in pH, total solids, total nitrogen : phosphorus : carbon levels has to be monitored critically for normal functioning of the biofloc system. The zero or minimal water exchange depends on removal/conversion of metabolic waste products which is dependent on the dynamic interaction among communities of bacteria, microalgae, fungi, protozoans, nematode, etc. These microorganisms which form the biofloc, help in water quality maintenance and recycling of wastes into high value food, naturally. Hence, biofloc turns out to be more efficient water conserving system than the traditional constant circulating water system, as no new water has to be incorporated daily for maintenance of microenvironment. A small technological intervention like Biofloc reduces the water requirement, which can be utilized for other enterprises. As there is efficient conversion and utilization of waste products the environmental pollution is drastically reduced.
Advantages of Biofloc system
Organic farming without usage of antimicrobials to control infections and pathogens
High quality animal product production for humans
Reduction in water utilization than traditional aquaculture
Eco friendly technology
Reduction in environmental hazard
Reduction in water pollution and water pathogens
Better land utilization for aquaculture due to closed/small system
Reduction in total feed cost
Reduction in high protein feed
Reduction in production cost
Cost effective natural feed production
Faster growth in cultured species
Better feed utilization and less wastage of feed
Increase in survival, growth and immune status of cultured animals
Disadvantages of Biofloc system
Critical monitoring during initial floc development
Maintenance of alkalinity
Extra energy expenditure for mixing and aeration
Inconsistent performance in sunlight exposed flocs
If unchecked, increased nitrate accumulation
With the growing human population and its demand for food the animal production should also increase at the same pace. The BFT is a promising aquaculture technique, utilizing the natural symbiosis of the various microorganisms for better feed utilization and conversion of waste products in to high value natural feed. The research and results obtained for Biofloc are very promising in long term to increase animal production organically, with least environmental hazard or pollution, in a cost effective, economy strengthening way.
Some additional, practical information and problems and their solutions are offered in following you tube videos
https://youtu.be/S3nN7x7ISkI; https://youtu.be/dzDgFapmr2M; https://youtu.be/luJhL2lCHE8; https://youtu.be/OXZGvwoBEt4; https://youtu.be/ctW2ZhPGRAM; https://youtu.be/kdgP0MhL5q8; https://youtu.be/XSuzoiiIJt0; https://youtu.be/PUL-a_pPmoo
List of Indian Institutes where Biofloc based aquaculture Trainings and Information is provided,
The Central Institute of Brackish water Aquaculture, Chennai (ICAR-CIBA)
The National Fisheries Development Board (NFDB)
123Assistant Professor, Department of Veterinary Physiology, College of Veterinary & Animal Sciences [MAFSU], Parbhani
4Assistant Professor, Department of Veterinary Medicine, College of Veterinary & Animal Sciences [MAFSU], Parbhani
Food and Agriculture Organization (2010) The State of World Fisheries and Aquaculture 2010. Rome: Food and Agriculture Organization, pp. 179.
Department of Animal Husbandry Dairying and Fisheries (2017) Annual report 2016-17. Ministery of Agriculture, Government of India, pp. 162.
Kuhn D.D., Lawrence A.L., Boardman G.D., Patnaik S., Marsh L., and Flick G.J. (2010) Evaluation of two types of bioflocs derived from biological treatment of fish effluent as feed ingredients for Pacific white shrimp, Litopenaeus vannamei . Aquaculture 303: 28–33.
Ju Z.Y., Forster I., Conquest L., Dominy W., Kuo W.C., and Horgen F.D. (2008) Determination of microbial community structures of shrimp floc cultures by biomarkers and analysis of floc amino acid profiles. Aquac Res 39: 118–133.
Tacon A.G.J., Cody J.J., Conquest L.D., Divakaran S., Forster I.P., and Decamp O.E. (2002) Effects of culture system on the nutrition and growth performance of Pacific white shrimp Litopenaeus vannamei (Boone) fed different diets. Aquacult Nutr 8: 121–137.
Crab R., Defoirdt T., Bossier P., and Verstraete W. (2012) Biofloc technology in aquaculture: beneficial effects and future challenges. Aquaculture 356: 351–356.