Fisheries is a very important economic activity and a flourishing sector with varied resources and potentials. Only after the Indian Independence, has fisheries together with agriculture been recognized as an important sector. Fish is crucial to a nutritious diet in many areas across the world. Fish is rich in protein and essential amino acids and also good source of calcium, vitamin A and B12 and omega-3 fatty acids. People irrespective of age who do not get sufficient nutrients from cereal-based diets, would be benefited from the inclusion of fish in the diet. Aquaculture not only supplies dietary essentials for human consumption, but provides excellent opportunities for employment and income generation, especially in the more economically backward rural areas.

India is one of the leading countries and major contributors to aquaculture production. Presently, the country ranks second in the world in total fish production with an annual fish production of about 9.06 million metric tonnes. Freshwater aquaculture contributes to over 95 percent of the total aquaculture production. According to FAO projections, Aquaculture production is to be reached 109 million tonnes in 2030, an increase of 32 percent (26 million tonnes) over 2018.The food and agricultural organization (FAO) predicted that the current level of consumption of aquatic foods is necessary to uphold due to the increasing global population. In order to increase aquaculture yields, the country needs additional resources. In addition to the problem of finding the resources, there are several other factors such as increasing operational costs, the high cost of land for culture, the high cost of commercial feed, disposal of wase sludge, discharge of effluent from aquaculture farms hinders the economic success or viability of commercial aquaculture.In aquaculture, the major cost during the entire production cycle has been contributed by feeding of fish. Similarly, 60-70 % of the variable cost involved in the operation was attributed to feeding alone which in turn reduced the farmer’s profit. Availability of land and water are other issues. Water availability is scarce in some regions and lands are expensive. These huge production costs have forced farmers to look for ways. By adopting this Profitable Method of Biofloc Fish Farming more aquatic foods can be produced by using fewer resources. These issues can be overcome by increasing the fish biomass per unit area and reducing the use of expensive feed ingredients or high protein feeds.

Biofloc fish farming is one of the best available methods today which is helping fish farmers to attain a wide range of objectives such as high output, low cost, sustainable growth, better income opportunities, less area, less maintenance cost etc. It has become very popular all around the word as an alternative to open pond fish farming. It is a low-cost way in which toxic materials for the fish such as Ammonia, Nitrate, and Nitrite can be converted into feed.Rearing of fish at high-density requires some waste management system. Biofloc is a waste treatment system at its core. It was developed to prevent diseases from incoming water to a farm.

Biofloc technology (BFT) is considered the new “blue revolution” in aquaculture since nutrients can be continuously recycled and reused in the culture medium, benefited by the minimum or zero-water exchange. It is a technique of enhancing water quality in aquaculture through balancing carbon and nitrogen in the system. Biofloc is defined as ‘the use of aggregates of bacteria, algae, or protozoa, held together in a matrix along with particulate organic matter for the purpose of improving water quality, waste treatment and disease prevention in intensive aquaculture systems’.

This technique is based on in situ microorganism production which plays three major roles:
(i) Maintenance of water quality, by the uptake of nitrogen compounds generating in situ microbial protein
(ii) Nutrition, increasing culture feasibility by reducing feed conversion ratio (FCR) and a decrease of feed costs
(iii) Competition with pathogens.

Bioflocs provide two critical services that are treating wastes from feeding and providing nutrition from floc consumption. Biofloc systems can work with low water exchange rates (0.5 – 1 % per day). This long water residence time allows the development of a dense and active microbial flocs. The microbial flocs thus formed are a source of protein for the shrimps, thus reducing the feed cost. This technology increases the profitability and business sustainability.

Biofloc system is a wastewater treatment which has gained vital importance as an approach in aquaculture. The principle of the technique is to maintain the higher C-N ratio by adding carbohydrate source and the water quality is improved through the production of high-quality single cell microbial protein. Biofloc technology converts unused feed and aqua animal feces into food in a culture system while exposed to sunlight creating a protein rich live feed. By converting excess matter into food again, the cost of feeding comes down.The main component of Biofloc is heterotrophic bacteria. These Heterotrophic bacteria consumes Ammonia, Nitrite converting it into protein. This can be consumed by fish then for growth. It works as actual feed for the fishes. Its nutritional values are also good.

The biofloc-based farming system is a new technology for the promotion of intensive fish production in a limited area. A person having small landholding (as small as 150-200 square metres of land) and having either municipal piped water supply or bore well water supply can establish this business with a small investment. This technology aims to support fish farmers and young entrepreneurs for livelihood support.

Main items required for Biofloc Tank Setup:

Biofloc system works best with species that are able to derive some nutritional benefits from the direct consumption of the floc. Biofloc system is most suitable for species that can tolerate high solid concentration in water and are generally tolerant of poor water quality. These species are wholly or partially filter feeders. Both shrimp and tilapia are excellent candidates, as they gobble up bioflocs, thereby dramatically improving the feeding efficiency and FCR of fish farming operation. Sensitive species will not thrive in this environment. The system is suitable for growing freshwater fish species such as Cat fish like Tilapia, Magur, Pangasius, Anabas and Common Carp. Nile tilapias are capable of absorbing suspended biofloc, being adapted to high stocking densities. Tilapias are able to efficiently utilize heterotrophic bacteria and are thus suitable for cultivation in biofloc systems.

Company	Contact	Country
Air Breathing fishes	Singhi (Heteropneustes fossilis)
Air Breathing fishes	Magur (Clarius batracus)
Air Breathing fishes	Pabda (Ompak Pabda)
Air Breathing fishes	Climbing Perch(Anabes testudineus)
Air Breathing fishes	Pangasius(Pangasius pangasius)
Non-air breathing fishes	Common Carp(Cyprinus carpio)
Non-air breathing fishes	Rohu(Labeo rohita)
Non-air breathing fishes	Tilapia(Oreochromis niloticus)
Non-air breathing fishes	Milkfish (Chanos chanos)
Non-air breathing fishes	Pacu (Piractus brachypomus)

• Fill the tanks with fresh water, from the source of well/ bore water and Start aeration and leave it for 24 hr with aeration. Water must be clean rather it hard to maintain into this culture. Due to low consumption of water, you don’t have to worry about water on a daily basis. Once it is full it will last for 6 month or one culture. Only you need 40-50 litre of water for 1000 litre tank capacity for every 7-15 days. This water will be lost when you drain your water to remove Sludge Every 7-15 days.

• Products needed for water Preparation:
1.Raw Salt (Non-Iodized) - TDS management
2.Caco3 - pH Management
3.Carbon sources (Molasses/ Liquid jaggery or other sources) - Ammonia Management
4.Probiotics - Bacteria Management

• Test for TDS after 24 hr of aeration. Required TDS parameter is 600-1200 PPM for fishes. If you are getting low TDS 300-500 ppm add 1 kg Raw salt and leave it for 3 hours, increases the TDS.Raw salt is the salt which is iodine free and no refining done after collecting from sea water. Don’t use Iodine salt as it will reduce the activities of floc. Raw salt can be applied to Biofloc tanks in the ratio of 1kg salt to 1000-liter water but make sure salinity must be maintained in this manner only not so high and nor low.

• If TDS is high, use CACO3 to reduce TDS level. Generally, Take 50 grams of CACO3 for 1000 liter of Water. IfTDS is too low it helps to boost your TDS level and take to normal percentage. It Works on both side both Low and high TDS level.

• Next step of water preparation, use Probiotic and Molasses Together. Add 50 grams of Probiotic and 100 grams of Molasses for 1000 liter of water. Calculate as your tank capacity, For 10,000 liter tank we need 500 grams of Probiotic and 1 kg Molasses. Put Molasses and probiotic into a Bucket and Mix well. Now your mix is Ready to add.After 3 days add 1 kg Molasses And leave it for 1 day. Don’t Stop aeration from the day we start.

Probioticsis a naturally occurring bacteria, applied in the beginning of the biofloc system could help in manipulating the microbial system. It creates and maintains high water quality to create an ideal environment for the better growth of aquatic animals. It oxidises ammonia to form nitrates. Enhances natural nitrification cycle to convert nitrates into Nitric oxide, Nitrous oxide and harmless nitrogen.

Feeding is an important control in achieving the proper C:N ratios that promote the uptake of ammonium from the water. In addition, effective feed strategies enable fish to utilize the recycled microbial protein, reduce costs and minimize residues. The recommended C:N ratio can be obtained by feeding with pellets of low protein content or by augmenting the feed pellets through the application of carbonaceous material such as molasses, cassava, wheat or other flours. Feed rations can be lower than those used in conventional tilapia ponds. With shrimp in BFT tanks, it was found that feed rations could be reduced 20 - 30 percent lower than the rates used in conventional systems.

The management of the carbon-to-nitrogen ratio (C:N) in BFT is normally divided in two phases:
(i) Initial and formation phase, utilizing a carbon-to-nitrogen ratio of 12–20:1 to promote and stabilize the heterotrophic community in BFT
(ii) Maintenance phase, utilizing a carbon-to-nitrogen ratio of 6:1, according to the total ammonia nitrogen (TAN) values

Initiallythecarbonsourceappliedbasedontheamountoffeedandtheproteinpercentageofthe feed applied, later during the culture period, as the floc level increase and available nitrogen source increases due to unutilized feed, excretion etc., and the carbon addition should be based on the TAN level in the culture system. As per the previous reports on C:N ratio, if the TAN level goes beyond 1mg/L, the carbon source addition is recommended with Have to maintain C:N ratio is 6:1 during the ongoing culture,
Calculation of carbon based on TAN:
For example, Ifyou have 1.5mg/L TAN is measured in 15000L tank

1.5 mg = 0.0015 gram
= 0.0015x 15000
= 22.5gram of TAN in 15,000 L tank

If you want to maintain the C: N ratio with 6:1
= 6 x 22.5 = 135g of carbon are required.

If you add rice flour as carbon source (Rice flour has 40% carbon content)
= 135/ 40x100
= 337.5 gram of rice flour to be added to maintain 135 g carbon.

The C/N Ratio Calculation is based on Fish Feed Protein Percentage and the below table shows the C/N Ratio of the fish feeds.

Protein Percentage (%) offish feeds	C/N Ratio
15	21.5
20	16.1
25	12.9
30	10.8
35	9.2
40	8.1

If you are using 25% protein feed then according to the above chart the C/N Ratio of 12:1 is fulfilling. As per the studies, the CN Ratio of 12-20:1 is more successful. It has been proved the CN Ratio of 12:1 does not require even water exchange. In a Biofloc system, it’s recommended to feed low protein feeds. You will have better control over Ammonia and the mortality rate will be less.

During the culture period, the water chemistry in the system should be monitored and maintained. Mainly few water quality parameters should be monitored on daily basis other should be monitored periodically like every 3 days once. Dissolved Oxygen, pH, Temperature, turbidity can be monitored twice a day, NH3, NO3, NO2 and TAN can be monitored on daily basis. Algal community, alkalinity, hardness salinity can be seen once a week. Floc volume should be maintained at 12-20 ml/L should be maintained. Total heterotrophic count can be monitored on every 3 days once. The levels of water quality parameters should be kept in optimal condition for retaining the fish health and avoid mortalities. Understanding of water quality parameters and its interactions in BFT are crucial to the correct development and maintenance of the production cycle.

Water Parameters	Optimal Range
Dissolved Oxygen	> 4. 5 ppm
Temperature	26-340C
pH	600 ppm
Settling solids (SS)	5-20 ml/L (Tilapia fingerlings) 20-50 ml/L (Juveniles and Adults’ fish)
Floc density	25-40 mg/l
Salinity	10-25 ppt
Ammonia	< 0.5 ppmt
Nitrite	< 0.3 ppm
Nitrate	150 ppm
Alkalinity	120-280 ppm

Oxygen consumption in intensive biofloc tilapia culture is rather high due to the respiration of the high fish biomass as well as the microbial community that metabolizes the organic residues.Water respiration in indoor biofloc systems is normally about 4 mg O2/L per hour. It is believed that aeration requirement of 1 HP of every 200-250 kg of biomass.However, the exact aeration rate needed for a given tank should be adjusted following on the stocking density, feeding rate, and early morning dissolved oxygen in shrimp ponds. Farm operators can usually use lower aeration at the start of the production cycle, then increase the aeration based on biomass.

Air pumps are useful for tank water aeration and filtration also Ideal for biofloc systems. In addition to the requirement for aeration, mixing is also very important, as the floc particles must remain in suspension in the water column. Maintaining proper water flow velocity is essential for optimizing biofloc systems and keeping microorganisms suspended in the water column. An additional benefit of aeration and mixing is the removal of gases from the water column, which can have a great effect on overall water quality. We need 24hr oxygen supply in our biofloc tank.

The pump pushes the air to the tank through PVC pipe and distributed through the air tube which is connected to the air stone at the end. Air stones help air to be distributed through the tiny holes making micro-bubbles in the water which help oxygen to dissolve in water evenly and push sludge from the bottom for maintaining floc at the surface.

Biofloc is a heterogeneous aggregate of suspended particles and variety of microorganisms associated with extracellular polymeric substances. It is composed of microorganisms such as bacteria, algae, fungi, invertebrates and detritus, etc. Each floc is held together in a loose matrix of mucus that is secreted by bacteria and bound by filamentous microorganisms or electrostatic attraction. In biofloc microbial systems, where bacterial density can reach 1 billion cells/mL, the bacteria stick together with other organisms and organic particles to form bioflocs whose particles range in size from 0.1 to a few millimeters. Such particles are easily assimilated by fishes like tilapia.

A good nutritional value is found in biofloc. The dry weight protein content ranges from 25 – 50 percent, fat ranges 0.5 – 15 percent. It is a good source of vitamins and minerals, particularly phosphorous. It also has an effect similar to probiotics. The amounts of protein stored in bioflocs are very significant. If only 50 percent of the TAN excreted by tilapia is assimilated and available as a fish feed, this process can add an amount of protein equivalent to feeding with 30 percent-protein pellets at a daily ration of 150 g/m3.

Floc volume is determined by using Imhoff cones is easy and cheap. Floc volume should be in the 10-50 mL/L range. Floc density can be adjusted by controlling the air flow rate to air lift pump.If floc density is too low, add low protein feed along with carbon source, and if it is higher than 50 ml/L, increase sludge removal by draining.

BT can lead to many benefits, including the following:

Apart from advantages biofloc system has few disadvantages:

• Beneficiary needs to submit the project report (PR) along with required documents including documentary evidence of availability of requisite land (either own/registered lease document to the concerned District Fisheries Office for further process. In case of leased land, proper registered lease document for a period of 7(seven) years from the date of submission of Self Contained Proposal (SCP) will have to be submitted.

• Project report (PR) with full justification & technical-economical details including the species to be cultured, capital cost and the recurring cost involved. Project report should also contain details of anticipated direct & indirect employment generation to local population, enhancement of fish production, specific time lines for implementation of project etc has to be furnished to District Fisheries Office (DFO).

• In case of Biofloc in Pond, the governmental assistance is restricted to (a) 2 units of 0.1 ha per individual beneficiary, (b) 2 units of 0.1 ha multiplied by the number of members of the group/society with a ceiling of 20 units of 0.1 ha per group/society in case of Groups of fishers and fish farmers i.e. fisher SHGs/Joint Liability Groups (JLGs)/Fisher Cooperatives etc. or those undertaken in a cluster/area approach.

• In case of Biofloc in tank, governmental assistance will be restricted to one unit of large or one unit of Medium or 1 of small BFT for individual beneficiary. Governmental assistance will be restricted to 2 units of large or 3 unit of Medium or 4 units of Small BFT per group/society in case they are taken up by Groups of fishers and fish farmers.