By-Praveen Shrivastava,CEO, Livestock Business Consultancy Services, Jamshedpur
Biofloc fish farming System: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. The technology has recently gained attention as a sustainable method to control water quality, with the added value of producing protein-rich feed insitu.The basic technology was developed by Dr.Yoram Avinmelech in Israel and initially implemented commercially in Belize by Belize Aquaculture. Biofloc farming technology used in Fish and Shellfish culture with limited or zero water exchange under high stocking density, strong aeration and biota formed by biofloc.The principle of this technique is the generation of nitrogen cycle by maintaining higher C: N ratio through stimulating heterotrophic microbial growth, which assimilates the nitrogenous waste that can be exploited by the cultured spices as a feed. It is a good source of vitamins and minerals, particularly phosphorous. It also has an effect similar to probiotics.The biofloc technology is not only effective in treating the waste but also grants nutrition to the fish and shellfish farming. It is an innovative and cost-effective technology in which toxic materials to the fish and shellfish such as Nitrate, Nitrite, Ammonia can be converted to proteinaceous feed. The technique involves addition of molasses as carbohydrate source in water. This carbohydrate facilitates higher growth of bacteria, fungi and single cell organisms in the water which helps in faster bio-chemical cycles such as Nitrogen cycle. So the water quality remains optimum for culture purpose. Moreover the floc of bacteria fungi protozoea are taken by fish as source of food. Biofloc contains more than 60% protein and it helps in better growth.1. Limit water exchange2. Organic residues accumulate3. Mix and aerate.4. Ideal conditions for bacteria5 Bacteria control water quality.6. Fish eat bacteria7. Feed is recycledBenefits of Biofloc culture system :• Eco-friendly culture system• It reduces environmental impact.• Improves land and water use efficiency• Limited or zero water exchange• Higher productivity (It enhances survival rate, growth performance, feed conversion in the culture systems of fish).• Higher biosecurity.• Reduces water pollution and the risk of introduction and spread of pathogens• Cost-effective feed production. • It reduces utilization of protein rich feed and cost of standard feed.• It reduces the pressure on capture fisheries ie., use of cheaper food fish and trash fish for fish feed formulation.Disadvantages of Biofloc Technology• Increased energy requirement for mixing and aeration• Reduced response time because water respiration rates are elevated• Start-up period required• Alkalinity supplementation required• Increased pollution potential from nitrate accumulation• Inconsistent and seasonal performance for sunlight-exposed systemsEquipment for Biofloc fish farmingFish Tank : This is the basic thing you will need to culture fish using Biofloc fish farming technology.Water : Obviously this most essential.TDS Meter/Salinity meter: To check Total dissolve solid in water and for checking Salt percentage you will need salinity meter.PH meter/Kit/Strip : For regular checking of water PH value as for biofloc fish farming best range of PH is 6.5 to 8.5.Alkalinity meter: PH test kits shows only values of Acid & Alkaline But doesn’t show alkalinity levels for this alkalinity meter is essential.Ammonia (TAN) test kit : For checking values of Total ammonia nitrogen (TAN) available in tank.Nitrite, Nitrate test kit : For checking values of Nitrite and nitrate available in tank.Dissolve oxygen test kit/ meter : For checking values of dissolve oxygen available in tank which is very much essential.Thermometer or Digital temperature meter : For checking values of temperature available in tank as ideal temperature for biofloc is 20 degree to 40 degree Celsius.Air blower/pump including air pipes, air stones, air tube, connectors etc : For proper aeration in Biofloc tank these items are very much essential.Imhoff cone with stand : For measuring floc in tank which is essential as over floc in tank will decrease oxygen level in tank.Power backup like generators, inverters etc : This is essential because in biofloc tank aeration needs 24×7 so for smooth aeration you will need power backup sysytem.Raw Salt : It is very much essential as without this fish can’t survive in Biofloc tank.Carbon source (Molasses, Jaggery etc.) : Another essential equipment for floc formation and depletion of Ammonia in Biofloc tank.Calcium Carbonate (CaCO3) : For balancing water PH in Biofloc tank.Probiotic : Bacteria found in powder forms.Fish Feed : For fish growth.Weighting Machine : You will need for calculating biomass and also during the time of Harvesting.Construction of Biofloc TankBFT ponds should be designed and constructed to enable aeration and mixing of the whole pond area/depth. The classical design is based upon a round pond concept with aerators inducing radial waterflow, or otherwise square or rectangular ponds where water flow is sort of radial, mostly in parallel to the pond dykes. In such cases, corners are rounded or cut, to minimize stagnant areas. A different approach is to construct the pond as a closed raceway, where water flow is directed by a solid or loose partition along and around the pond.Ponds should be constructed to prevent dyke erosion, to enable complete drainage of water, to minimize area of sludge accumulation and to facilitate ease of draining of sludge. Lining the pond is highly recommended. Ponds should be lined with plastic or hard solid materials. Drainage and harvesting openings should be constructed in low- lying locations and coordinated with water flow regime.An intensive BFT pond has to be planned bearing in mind the need to provide proper aeration to all parts of the pond, mixing the water to minimize anaerobic sludge accumulation and to enable Periodic drainage of the sludge both during the crop and between crops. Additionally, designs should facilitate efficient harvest and easy feeding.Intensive ponds should not be too large. The biomass in the ponds is high, thus controlling large Volumes of water is difficult, harvesting of too high biomass is complicated and the risk of holding dense fish or shrimp populations in very large reservoirs may be too high. The risk of losses if something goes wrong in large intensive ponds is very high. 1he typical size range of intensive ponds is normally in the range of 100-20,000 m2 (0.01-2 ha). The common size of intensive BFT fish ponds is 100- 1,000 m2 while the typical size of intensive BFT shrimp ponds is 1,000- 20,000 m2 (0.1-2 ha). The depth of ponds is in the range of 1-2 m. The advantage of deep ponds is their high heat buffering capacity, which helps to avoid over-heating or over-cooling during the diurnal cycle. In addition, the deeper water column minimizes contact of the surface water to pond bottom anaerobic conditions and allows a deeper water column for feeding and biological processes. However, constructing deeper ponds demands a higher investment and, in cases of limited gradient to the drainage base, makes drainage and harvests more of a problem.Additional advantages of lining are the ease of cleaning pond bottom in between cycles and possibly more efficient mixing and utilization of feed residues sinking to the bottom. It is interesting and important to note that the nature of organic matter accumulating on the pond bottom differs between lined and earthen bottoms. In earthen ponds, the organic residues mix with the soil, forming a rather stable complex, in comparison to highly degradable, unstable and bio-reactive organic resides that accumulate on the lining. This difference affects pond management: in earthen ponds, organic Matter accumulates over a period covering several cycles and has to be periodically removed. In the case of lined ponds, organic deposits should not accumulate, and due to the high reactivity they vigorously affect chemical and biological processes in the pond and may cause a real problem.The bottom should be smooth to ease draining and cleaning.Most BFT ponds design is based upon radial aeration of the pond. In most cases round ponds are managed, with aerators placed parallel to the dykes, leading to a radial water flow pattern. Round ponds are the most common design tor small ponds, Used in hatcheries and some production units.Building larger round ponds is more difficult (digging, utilizing land, lining) and rectangular or similar design is more common. In many cases the corners in these types of ponds are rounded or smoothed, in order to enable undisturbed flow of water and to minimize the area where flow and aeration are limited.Radial flow ponds (round, square, rectangular) tend to collect the sludge at the center ot the pond. to help concentrate the sludge at the center, the center of the pond should be the deepest part of the pond and the pond should slope toward the center. Operating a BFT pond, two opposing goals should be kept in mind. On the one hand, it is desirable to trap the sludge in a small drainable area. However, we need to keep high enough active suspended matter in the pond (in the order of a few hundred mg/l). 1n order to keep from getting too much organic residues in the center and to achieve enough active suspension, it is necessary to get some water directed onto the central region, so as to re-suspend the settled particles. This flow pattern raises particles into the water and in a way separates larger heavy particles that stay in the center and finer light particles that are re-suspended. The re-suspension brings organic particles away from the pond bottom and upward toward the aerobic water column. The re-suspension may be achieved by placing aspirator pump aerators directed toward the center, placing air-lift pump(s) or upward flow aerators above the center.A number of accessories are essential or beneficial for the successful operation of intensive BFT ponds. Intensive ponds carry a high biomass and strongly depend upon aeration. A fault in the aeration system may be critical and may lead to a complete failure of a pond or even of the whole farm. Thus, a fail-safe operation of the aeration system is essential. For this, one needs a reliable electricity supply as well as a reliable back-up of all electrical components, such as generators, circuit components and parts. In addition, back-up of aerators and o:her spare parts must be available. Appropriate staffing including nights and weekends as well as alarm systems and/or automatic switching to backup systems are an integral part of sustainable intensive systems.Salinity in Biofloc fish farmingThe word salinity may be new to many but actually in Biofloc while water preparation we use raw salt and the mixture is called as salinity. Raw salt is the salt which is iodine free and no refining done after collecting from sea water. We can’t use Iodine salt as it will reduce the activities of floc. Raw salt can be applied to Biofloc tanks in 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.Why Salinity?It holds dissolve oxygen level in water, maintain dissolve oxygen not high and nor low.It helps in floc formation.It controls NH3It helps in reducing Nitrite.It helps in maintaining PH level.It reduces stress to fish.It also helps in digestion of fish.PH in Biofloc fish farmingThe term “pH” is a mathematical transformation of the hydrogen ion (H+)concentration; it conveniently expresses the acidity or basicity of water. The lowercase letter “p” refers to “power” or exponent, and pH is defined as the negative logarithm of the hydrogen ion concentration. Each change of one pH unit represents a ten-fold change in hydrogen ion concentration. The pH scale is usually represented as ranging from 0 to 14, but pH can extend beyond those values. At 25 °C, pH 7.0 describes the neutral point of water at which the concentrations of hydrogen and hydroxyl ions (OH-) are equal (each at 10-7 moles/L). Conditions become more acidic as pH decreases and more basic as pH increases.The pH of freshwater ecosystems can fluctuate considerably within daily and seasonal timeframes, and most freshwater animals have evolved to tolerate a relatively wide environmental pH range. Animals can, however, become stressed or die when exposed to pH extremes or when pH changes rapidly, even if the change occurs within a pH range that is normally tolerated.PHAction4Acid death point4 to 5Breeding stopped4 to 6.5Slow growth6.5 to 8.5Ideal condition for fish growth8.5 to 10Slow growthAbove 11Alkaline death pointManaging Problems with Low pHApply CaCO3Managing Problems with High pHHigh pH can be corrected simply by adding an acid to increase that concentration. However, “high pH” also describes the net result of many individual processes that add or remove carbon dioxide. Reducing pH with an acid does not alter these processes and, therefore, cannot address the underlying causes of high pH. So while adding an acid may temporarily reduce pH, high pH will probably occur again unless other environmental conditions also change.The long-term solution to high pH problems in ponds is to alter pond biology so that the net daily carbon dioxide uptake is near zero. This can be done by reducing photosynthesis or increasing respiration.Increasing the calcium level in a pond by adding gypsum may help reduce the occurrence of high pH and benefit animals by helping them respond better physiologically to pH extremes and other environmental stressors.It is difficult to reduce pH significantly by adding an acid to the water because pond waters are usually buffered by bases of the alkalinity system. Relatively large amounts of acid are therefore needed to achieve a meaningful decrease in pH. Also, adding an acid to water is only a short-term solution because it addresses the result rather than the cause of the problem, which is rapid plant growth.An emergency treatment that quickly reduces high pH is the application of alum (aluminum sulfate). This is a safe, relatively inexpensive chemical that reacts in water to form an acid. Besides reducing pH, alum also flocculates and removes algae by sedimentation, thus decreasing algal biomass and reducing photosynthesis. Alum may also help to reduce pH indirectly by removing phosphorus—an important nutrient for plant growth.Alkalinity in Biofloc fish farmingPH test kits shows only values of Acid & Alkaline But doesn’t show alkalinity levels present in water. In Biofloc tank Alkalinity must be 100+ mg/L which can be tested using Alkalinity tester because carbon and Biocarbon both are essential for water.Free Ammonia-Nitrogen in Biofloc fish farmingNitrogen enrichment of the water is a common process in all aquaculture systems. The extent of this Process rises with the increase of biomass and feeding. Both ammonia (NH3) and nitrite (NO2) are Toxic and may dramatically affect fish growth, health and existence. Means to remove theese species or transform them to non-toxic nitrogenous species are essential in high density systems. Major processes discussed here are algal uptake of inorganic nitrogen and nitrification.Fish are fed by natural and formulated feeds containing protein, usually in the range of 30-40% protein. However, fish use much of the protein as a source of energy, by Oxidizing it and using the energy stored in the proteins (Hepher, 1988). A major end product of this metabolic route is the formation of ammonium and ammonia and its excretion through the gills to the surrounding water. An additional source of total ammonium nitrogen, TAN, in the pond, is the decomposition of organic matter, especially decomposition under low oxygen conditions, such as those existing in the pond bottom.It is obvious that unless ‘TAN is removed or converted to other forms of nitrogen, a significant and dangerous rise of TAN will take place within a few days. Ammonium is an end product of protein bio-degradation. Ammonium or mostly its un-ionized Species- ammonia is toxic. Fishes excrete TAN by the diffusion of ammonia through the Gills, fulfilling a similar role as the kidneys. When ammonia concentration in the water is high, outward diffusion is slow and ammonia is built up within the fish, affecting the central nervous system and causing other damages to the organism. Chronic exposure to ammonia leads to reduced growth and greater susceptibility to disease. The lethal level of un-ionized ammonia is in the range of 0.2-2 mg/1, a bit different for various fishes. It has to be noted that ammonia toxicity increases when Oxygen concentration is low.TAN is made of two species, the ammonium ion, NH4+, that dissolves in the water and is not Volatile, and the un-ionized species NH3 that can be volatilized out of the water. The two species are in a state of equilibrium, as determined by the pH.At pH 9.3, 50% of TAN is in the form of ammonia (at pH = 9.3, (NH3) = (NH4+). When pH is low, (H+) is high), most of the TAN is stored in the water as NH4+, the ammonia effect is lower and it does not volatilize. When pH rises, the fraction of NH3 rises. Ammonia toxicity is higher at high pH values (e.g. in top layers of pond water during afternoon time) One might expect a release of ammonia to the atmosphere when water pH is high. However, when free ammonia is high, a severe danger of toxicity exists.’free’ versus ‘ionized’ ammoniaFree ammonia (NH3-N) and ionized-ammonia (NH4+-N) represent two forms of reduced inorganic nitrogen which exist in equilibrium depending upon the pH and temperature of the waters in which they are found. Of the two, the free ammonia form is considerably more toxic to organisms such as fish and, therefore, we pay considerable attention to the relative concencentration of this particular contaminant. Lastly, this free ammonia is a gaseous chemical, whereas the NH4+ form of reduced nitrogen is an ionized form which remains soluble in water.Means to control inorganic Nitrogen Accumulation:Minimizing nitrogen accumulation in Biofloc technology systems is possible through the control of carbon to nitrogen ratio, and the assimilation of inorganic nitrogen into the microbial protein discussed in the following chapter. In addition, as discussed later, Bioflocs contain nitrifying bacteria and seem to provide proper conditions for nitrification, even in systems contains organic matter concentrations.Important : Adding acid in case of an acute rise NH3, to slightly lower the pH is sometimes a good emergency measure to save the fish. Yet, be careful when adding concentrated acid not to over-shoot, acidify the pond water and eventually kill your fishNitrite and Nitrate in Biofloc fish farmingAnother toxic inorganic nitrogen species is nitrite- NO2. NO2 is an intermediate product of nitrification. When nitrification gets to a steady state, nitrites are promptly oxidized to nitrates- NO3, a non-toxic species. However, nitrite may accumulate during the onset of the nitrification process or as a result of improper pond aeration conditions (Note: A rise of NO2 concentration in the pond may be an indication of insufficient aeration or an indication for the accumulation of sludge and the creation of anaerobic pockets). Nitrite entering the blood stream oxidizes the iron in the hemoglobin molecule from Fe++ to Fe+++ Changing the hemoglobin to methemoglobin and poisoning the respiration process. Nitrite Crosses the gill membrane by the same mechanism normally used to transfer chloride. Thus, When chloride concentration is high (10-20 times higher than NO2, concentration), chloride competes with nitrite uptake and nitrite toxicity is reduced. Thus, NO, toxicity to shrimp growing in marine water is lower than that to shrimp growing in brackish water .The different aspects of inorganic nitrogen control were reviewed by Crab and co-workers, (2007). The critical factor relation to the potential damage of nitrogen buildup in the pond is the rate and capacity of mechanisms removing nitrogen out of the pond or transforming the toxic ammonia (and nitrite) into non-toxic components. Removal of the inorganic species is essential to maintain pond productivity, especially when intensity is increased.Both carbonaceous and protein rich components of the feed are metabolized, releasing TAN and carbon as CO2. The emitted CO2, reaches equilibrium with the air and excess CO2 is volatized and does not accumulate over time in the water. There are no similar rapid mechanisms to remove the equivalent TAN, from the pond system.Nitrate is not toxic, unless it is present in very high levels- more than 100’s mg/L.The oxidized nitrite and nitrate forms produced by the oxidation of reduced nitrogen (via nitrification) can also impose a toxic impact, although these forms are considerably less potent. First, although nitrites can not only be toxic but also mutagenic, this partially oxidized compound rarely reach levels sufficiently high to cause any problems (i.e., because it is readily oxidized by Nitrobacter bacteria to form nitrates). Nitrates may also impose their own form of toxicity, but they are many times (i.e., about 10 to 100) times less dangerous to fish than is free ammonia. Even then, if the levels of nitrates does reach excessively high levels, it can still kill the fish. Fortunately, though, nitrates are the form of nitrogen that plants love to eat….and nearly all plants love nitrates. Next to carbon dioxide, nitrogen is the highest element on their list of essential growth ingredients. Without nitrogen (nitrates), therefore, these plants simply won’t grow. Give a plant plenty of nitrogen (along with plenty of light, water, CO2, and about a dozen other trace elements), and it will then grow to be big and strong. It also locks that nitrogen up in its leaves and stems, removing them from the food chain.C:N Ratio in Biofloc fish farmingBacteria fed with carbonaceous substrates take up nitrogen from the water, because it is required for producing protein. By doing so, they reduce the concentration of inorganic nitrogen (especially TAN) in the water.When bacteria are fed with organic substrates that contain mostly carbon and little or no nitrogen (sugar, starch, molasses, cassava meal etc.), they have to take up nitrogen from the water in order to produce the protein needed for cell growth and multiplication.Bacteria and other microorganisms use carbohydrates (sugars, starch and cellulose) as a food, to generate energy and to grow:The addition of carbohydrates is a potential means to reduce the concentration of inorganic nitrogen in intensive aquaculture systems. By adding carbohydrate to the water, one forces the microbes to immobilize any inorganic nitrogen present in the water, preferably to immobilize TAN. This process is relatively fast, if the availability of the carbonaceous substrate added is high.Pond operators in Thailand used to keep bags of cassava meal to be used when cloudy days lead to the dangerous rise of TAN in the pond. Others use molasses addition when TAN concentration rise.A farmer in Israel, having easy access to a bakery, used spoiled flour addition when ammonium level in the pond rose.WARNING: Adding large rations of carbohydrates at once may lead to high oxygen consumption oxygen deficiency . It is better to apply it using partial additions and to monitor oxygen along this process.A different, pro-active approach is to add the right amounts of carbohydrate with the feed in order to prevent un-wanted TAN increase and to optimize the process. One has to estimate the amount of carbohydrate that has to be added in order to immobilize the ammonium excreted by the fish or the shrimp in real time.A partial water exchange, sedimentation or removal of sludge reduces the ammonium flux in amanner that can be calculated or estimated. In zero exchange ponds all the ammonium remains in the pond. Carbohydrate addition needed to assimilate the ammonium flux into microbial proteinsAn approximate calculation of the C/N ratio of different feed or feed mixtures is rather simple:1. The amount of carbon in the feed is very close to 50% of the total feed weight (almost all feed materials have about 50% carbon).The amount of protein is the protein percentage times the feed component(s) that contains protein and the amount of nitrogen is protein x 0.155 (on the average, 15.5% nitrogen in protein)C/N is obtained by dividing C (from a) by N (from b).Example:Pellets containing 40% protein:C-500 g/kg feedN: Protein= 400g/kg feed,N = 62 g N/kg feed (Protein x 0.155)C/N = 500/62 = 8.06In practice the calculations as above are used as a starting point, but the exact amount of carbon to be added has to be re-calculated following thedetermination of TAN concentration in the water. In cases when there is a low level of TAN, you should lower carbohydrates addition and if TAN is high or increasing, application rate has to be raised. This is a rather simple and straight forward control process.3 Basic parameters one should know are the protein percentage and the CN ratio of the feed. Protein percentage is given by the feed producer. The overall CN ratio of the organic substrates in the pond has to he adjusted taking into account the C/N ratio of the feed. The C/N ratios of differentC/N ratios of feed materialsProtein content %C/N1521.52016.12512.93010.8359.2408.1Aerators and Aeration in Biofloc fish farmingAeration is a basic means of management and control in BFT ponds. A proper aeration system is essential for the success these ponds. The aeration system is needed in order to supply oxygen, to mix the water and to control bottom2 sludge accumulation.Aerators of different types are used to cover oxygen deficits. Number, capacity and deployment of aerators are essential for proper management.Aeration is an essential means to achieve higher yields in ponds. Aeration systems are designed to achieve several goals:Supply oxygen to cover Oxygen consumption and to overcome oxygen limitations and thus enable higher stocking growth and yields.Distribute the oxygen in the pond, (1) horizontally and (2) vertically.Mix water and sediment – water interface.Control sludge coverage, location and drainage.It is important that aeration system will be designed, deployed and operated so as to achieve all the goals mentioned above as much as possible, in addition to merely supplying Oxygen.Oxygen limitations lead to reduced production, stress, disease and, in some cases, mortality. In general, sensitivity to low oxygen is different in shrimp and fish ponds. Shrimp are generally more sensitive in this respect than some fresh water fish and depend more on conditions at the bottom of the pond. Oxygen concentration in saline water is lower than that of fresh water (Boyd and Tucker, 1998; Fast and Boyd, 1987). In addition, oxygen saturation is lowered with the increase in temperature.As a very first approximation, oxygen balance can be estimated by knowing the feed addition to the pond. Daily feed addition in grow-out ponds is usually 2-3% of fish body weight.Difuscd air systems: These systems, used mainly in small tanks and ponds, are based on the release of small air bubbles to the water. The basic operative units are diffusers, made of ceramic air stones, porous rubber tubes and others, connected to a blower releasing a stream of small air bubbles rising in the water column. The principle of the diffused air systems operation is the same as that of the paddle wheel aerator, generating a large air-water interface. Yet, in this case it is the sum of air bubbles surface rather that water droplets ones. The efficiency of the diffused air systems rise with the decrease of the bubble size, yet, the smaller pores needed to achieve this, increase friction, required air pressure and power usage. Another factor affecting the efficiency of these systems is the contact time among the bubbles and the water. Thus, the efficiency of such systems in shallow water systems is very low. An improvement of diffused air systems increases, if the air tubes are placed in a bore-hole in the pond. Placing the air outlet in a few m. deep bore-hole may raise the oxygen transfer efficiency by several folds.A unit that may help aeration though rarely used in aquaculture is the “pond water circulator”. The water circulator consists usually of a propeller, usually operated by a submersible electrical pump. The circulator is pushing water horizontally, in most cases to one direction. A very low pressure is needed to push water horizontally (no pressure gradient). Thus, high volume of water can be pushed, using a relatively low pressure.Temperature in Biofloc fish farmingFor fish farming in Biofloc ideal temperature is 20°C to 40°C, Below 20° C less chance of floc formation Some bacteria can grow in 15° C also. Above 40°C there is chance of floc to die. Always try to install a thermometer or digital temperature meter to Biofloc tank for monitoring temperature. Try to avoid farming during winter season, if you want to do then manage the temperature above 20° C by installing water heater, or make a poly house etc. to control temperature but these processes are costlyCarbon source in Biofloc fish farmingSimple sugars,and complex carbohydrates are commonly used carbon sources for BFT, but in many countries that, complex carbohydrates can be much cheaper. However, this source is less soluble than simple sugars and thus cannot be quickly utilized by bacteria-producing flocs. This can consequently delay the removal of ammonia leading to deteriorated water quality. Therefore, among these tested carbon sources for the initial set up of BFT, sugars, Jaggery appear to be more appropriate.Bacteria and probiotic in Biofloc fish farmingFCR in Biofloc fish farmingThe feed conversion ratio is an indicator that is commonly used in all types of farming, as well as in the field of research. It can provide a good indication of how efficient a feed or a feeding strategy can be.In the context of aquaculture, the F.C.R. is calculated as follows: F.C.R. = Feed given / Final Weight- Initial Weight.In other words, the F.C.R. is the mathematical relationship between the input of the feed that has been fed and the weight gain of a population.Its calculation requires the following variables:The initial biomass – i.e. the number of fish in a farm population, multiplied by their individual weight — of the production unit under study (pond, cage, pool…);The final biomass of the same production unit;The amount of feed distributed.FCO in Biofloc fish farmingFCO means Fermented carbon organic. In this technique we add activated bacteria in Biofloc tank and then apply daily. By FCO technique we regularly add probiotic and carbon source to tank. By doing this we are maintaining strong bacteria to our tank all time also it enhances growth of fish.How to Prepare FCO:50 gm of Probiotic powder.600 gm Molasses600 gm Rae Salt (iodine free)20 liter waterFor fast activation of bacteria keep the container air tight. If not so hurry then without air tight give aeration floc will be activated within 7-8 days and you can notice orange color when floc activates. Add 5-7 liter of FCO in tank after sometimes you can add fish seeds. Remaining FCO apply daily 500 ml. Apply in this ratio every month before harvesting on 10 days gap of every month.For preparing FCO we use Carbon source and raw salt. For preparing FCO if we apply salt or Molasses more than 600 gm i.e, 700 gm and 600 ml i.e, 700 ml there is no harm but apply correct probiotic ratio.Disease in Biofloc fish farmingSeed selection, Sanitize & StockingSludge control in Biofloc fish farmingSludge accumulation cannot be avoided, yet, aeration and mixing lead to re-suspension and recycling of sludge in the various biological food chains. Excessive sludge accumulation has negative effects on fish growth and health. One essential control is periodical sludge drain-age. Sludge can be effectively drained if it accumulates on the pond bottom, in a location from which one can remove it using strong water current. In radially aerated ponds this location is on a drainage pit at the center of the pond.Efficient sludge removal demands a fast water flow that will effectively pull out the sludge from around the water outlet, a flow that can be obtained by lowering a stand pipe in the drainage canal. You drain the sludge as long as the outgoing flow is black-brown and you should stop the flow once you get clear water. Usually it takes 1-2 minutes.Drainage of sludge in intensive shrimp ponds is required toward the end of the cycle, when feeding is high. By that time, a weekly or bi-weekly drainage is recommended. With intensive fish ponds or very intensive shrimp Ponds the generation of bioflocs and waste is way too high to be suspended in the water, thus a large quantity of material settles and accumulates at the pond bottom. Daily or even twice daily Sludge drainage is required.Oxygen and pond bottom conditions monitoringOxygen should be monitored at least daily. If oxygen level is lower than the set value for the cultured animals, more aeration or longer duration of aeration should be supplied.As a rule, daily oxygen monitoring should be made at the same hour(s), in order to get comparable values. Pond operators are advised to periodically check oxygen at different locations and depths in the pond, to get an idea on the pond uniformity, existence of poorly aerated regions and to better know your pond. Looking on the water flow pattern in the pond, one can identity regions in the pond where water flow in limited. Oxygen supply in such regions may be limited! Additionally, sites where water is stagnant are susceptible as sites where bottom sludge accumulate. Development of sludge accumulation sites may be causative to fish stress, disease development and poor growth. Farm operator should be aware of this and check accumulation of sludge in such sites.The pH and the alkalinity should be maintained at conventional levels. Alkalinity should be above 50-100 mg as CaCO3/l and pH should be 7-9. Alkalinity and pH are usually stable in BFT ponds though there might be a need to add alkalinity in cases of high stocking density (Ray et al., 2009; Wasielesky et al., 2006). Nitrification is a major process leading to significant alkalinity consumption and to lowering of the pH. Systems, where the major inorganic nitrogen control is based upon nitrogen immobilization, are typically rather stable in respect to alkalinity and pH, in contrast to systems where intensive nitrification is taking place.Monitoring and control of Biofloc densityThe presence of flocs can be observed by taking a water sample in a transparent container and looking at the presence of suspended particles. Biofloc concentration can be simply evaluated using calibrated Imhoff cones.The cone should be filled with 1 liter water (sampled in front of an aerator in the stream of moving water to ensure representative mixed water sample) and let to stand still for 15-20 minutes (a suitable stand can be used to hold the cones). The volume of the settled floc volume is read following this period. In many cases, flocs are small and hardly seen when the water is sampled, but develop to large flocs in a few minutes. Leaving the cone for time periods longer than about 20 minutes results in gas formation within the floc plug and re-suspension of the particles. Typical floc volumes are a 2-40 ml/l in shrimp ponds and up to 100 ml/l in fish ponds.The presence of bioflocs in the pond is essential as means to control water quality (Ammonia, nitrite, excessive organic metabolites) as well as to facilitate the recycling of feed wastes toward edible microbial proteins.TAN could be controlled by heterotrophic activity even when floc volume was 2-5 ml/I.When floc volume is lower than 2 m/l (shrimp) or 5 m/I (fish) in advanced stages of culture, it is advisable to organic matter (molasses or other). However, floc volume above-15 ml (shrimp) or ~ 25 ml (fish) ) may be too high. floc volume leads to increased biological oxygen demand (BOD), demanding an un-nceded increase of pond aeration. possible to determine tit gross protein in the bioflocs, Heavy load of suspended matter can lead to clogging of gills. Excessive flocs should be drained and in some cases the water exchange rate should be raised.Step by step guide for culturing fish in BioflocWash the container with soap or with cleaning agent after that wash with Potassium permanganate(KMnO4).Dry the Container to free from harmful BactriaFill water with 50% height (Try to add water from underground if not possible then add from natural pond water, River not mineral water) – Check the TDS of the water.TDS level up to 400 is ok.Give aeration by aerator pump for whole day and continue ( Minimum 2 days to if any issue in PH level of water, and stable the TDS of water)Add sea salt (not iodized salt) 1kg salt / 1000 Liter water gradually to rise the TDS level and salinity level of water. After adding sea salt TDS value may be different in different water like underground water TDS will not same compare to natural pond water So, no need to worry about TDS values just maintain the ratio of salt in water ie, 1kg salt / 1000 Liter.Add CaCO3 (Calcium Carbonate ) 1 tsp / 1000 litre of water in the afternoon. – OPTIONAL It is applicable if your PH of water is below 6. If more then 6 it is not applicable. (Standard PH of water is 6.5-8.5 for biofloc)Add probiotic to water as directed by the probiotic manufacturing company by mixing it with the Carbon Source (Molasses, Sugar etc.). Otherwise you can apply probiotic by preparing FCO.Let aerator for 3-8 days until floc produce. Generally floc produce in 6-10 days.Another way for preparing floc is Using FCO(Fermented carbon organic) and it is the best for those who want to save account balance.
