Ten Easy Steps Towards Biofloc Production of Shrimp or Tilapia

Based on interviews with some of the earliest developers and\r\nadopters of biofloc, including Djames Lim from Singapore (CEO of the Lim Shrimp\r\nOrganization), Khoo Eng Wah from Malaysia (managing director of Sepang Today\r\nAquaculture Centre), Barkah Tri Basuki from Indonesia (Founder of Banglele\r\nIndonesia) and Dr Nyan Taw from Myanmar (senior shrimp farming consultant), The\r\nFish Site presents a practical 10-step guide to help you incorporate biofloc\r\nprinciples in your shrimp or tilapia operations.

The costliest factors in aquaculture are high-quality feeds,\r\nfiltration systems and the investment needed for ample space to grow target\r\nspecies. With continuously rising production costs, farmers and researchers are\r\nlooking for alternative ways to produce more seafood while utilising fewer\r\nresources.

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Originally conceived as a natural way to clean water,\r\nbiofloc systems are becoming increasingly popular as a low-cost means of\r\ncleaning the culture water of fish and shrimp farms while simultaneously\r\nproviding an additional source of feed. Best of all, implementing biofloc\r\nprinciples requires little investment – as only sunlight, a carbohydrate source\r\nand plenty of aeration are needed.

Biofloc systems bank on photosynthesis to convert uneaten\r\nfeeds, faeces and excess nutrients into food. While breaking down toxic ammonia\r\nand nitrates, both primary-producing autotrophic and heterotrophic bacteria\r\nmultiply to attract an ever-growing host of organisms – including diatoms,\r\nfungi, algae, protozoans and various types of plankton. Loosely bound by\r\nbacterial mucous, most of these floating clumps or “flocs” are microscopic.\r\nLarger aggregations can be seen by the human eye, resembling brown or green\r\nsludge. Though not too appealing for humans, this is a scrumptious smorgasbord\r\nfor fish and shrimp.

By recycling proteins, biofloc systems overcome concerns\r\nassociated with high animal-stocking densities and low filtration capacity –\r\nlike decreased water quality and increased risk of disease outbreaks. In\r\ntraditional farming systems, only about 25 percent of the protein content of\r\nfeeds are actually utilised by farmed species. By converting ammonium into\r\nmicrobial proteins that can be consumed by filter feeders, biofloc systems are\r\nable to double this figure, saving farmers big money. Biofloc systems reduce\r\nthe spread and effectiveness of pathogens while simultaneously improving fish\r\nhealth through better water quality and bolstered feed availability. As such,\r\nbiofloc systems can give us a natural way of producing more seafood\r\nsustainably, while concurrently improving farm profitability.

More of Asia’s top shrimp-industry players are shifting to\r\nbiofloc. As Djames Lim, CEO of one of the largest shrimp farming operations in\r\nthe region, explains: “Without biofloc our company wouldn’t be able to achieve\r\nits ambitious growth rates without compromising environmental integrity and\r\nanimal-welfare principles. This system is a win-win situation for all\r\nstakeholders.”

It’s important to understand that biofloc systems and their\r\nunderlying principles are relatively new and complicated aquaculture concepts.\r\nThere are still many unknowns and much remains to be discovered. We encourage\r\nreaders to conduct further research and to share their experiences to maximise\r\neveryone’s chances of success. And don’t forget to check out the training\r\nreference section at the end of the article for some very useful links.

Step 1: Tank or pond\r\nset-up

Though it’s possible to convert traditional fish ponds\r\nwithout any liner into a biofloc system, it’s a challenging task. Microbes,\r\nminerals and heavy metals naturally based in the soil easily influence the\r\nparameters of the pond water and can affect the natural processes underlying\r\nthe biofloc system.

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As Khoo Eng Wah, managing director of the Sepang Today\r\nAquaculture Centre (STAC) in Malaysia explains: “For those new to biofloc, it’s\r\nbest to start with lined ponds, concrete ponds or indoor tanks wherein soil has\r\nno influence over water parameters or biofloc processes.” In most tropical\r\ncountries, indoor systems have a big advantage. “As we experience heavy\r\nrainfall, alkalinity and pH are easily affected in outdoor systems. Covered\r\nponds are good options.”

Indoor tanks or raceways can be used as well, but without\r\nthe presence of natural sunlight, algae won’t grow sufficiently or won’t grow\r\nat all – creating a biofloc system based solely on bacteria. These so-called “brown\r\nbiofloc systems“ are brown in colour and are discussed in more depth\r\nlater (Step 7).

If you use large ponds you should instal bottom drains to\r\noccasionally remove excess sludge. This is especially important when adding\r\ncarbohydrates on a regular basis, which adds considerably more sludge to the\r\npond (Step 4). A second option is to use biofloc reactors to accelerate\r\nthe conversion of pond sludge to bioflocs.

Step 2: Aeration

After you have selected the right pond or tank set-up, it’s\r\ntime to work on the aeration system. All biofloc systems require constant\r\nmotion to maintain both high oxygen levels and to keep solids from settling.\r\nAreas without movement will rapidly lose oxygen and turn into anaerobic zones\r\nwhich release large amounts of ammonia and methane.

To prevent this, every pond, tank or raceway system needs a\r\nwell-planned layout of aerators. Ponds typically use paddlewheel aerators.\r\nBiofloc systems require up to 6mg of oxygen per litre per hour and it is\r\nrecommended to start with at least 30 horsepower of aerators per hectare. But,\r\ndepending on the intensity and productivity of the system, this number can\r\nreach as high as 200 horsepower per hectare (See table 1 from the Southern Regional Aquaculture Center further\r\non).

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Paddlewheel aerators should be installed strategically so\r\nthat a current is created in the pond. You also need to regularly move some of\r\nthe aerators to ensure solid particles won’t settle in areas with little or no\r\ncurrent.

Step 3: Pre-seeding\r\nbeneficial microbes

To accelerate the development of your biofloc system and\r\nstabilise your pond faster, it is advisable to pre-seed the culture water. This\r\ncan be done by adding a number of commercial or homemade recipes to the culture\r\nwater. INVE and VINNBIO are two of the better-known\r\ncompanies that provide starter cultures for various probiotic microbes, but\r\nthere are many locally produced brands available across Asia as well (just\r\ncheck out online forums or Alibaba).\r\nA simple homemade recipe to quickly produce probiotic and prebiotic microbes\r\nuses wheat pollard and Red Cap 48 (a\r\nlocal product from South-East Asia) mixed in a closed drum and left to ferment\r\nfor 48 hours, after which the contents can be added to the pond.

Step 4: Species\r\nselection and stocking densities

Though most species would benefit from the improved water\r\nquality of biofloc systems, you want to select species that best benefit from\r\nthe extra proteins generated, by feeding and digesting the bioflocs themselves.\r\nThese species are wholly or partially filter feeders. Both shrimp and tilapia\r\nare excellent candidates, as they gobble up bioflocs, thereby dramatically\r\nimproving the feeding efficiency and FCR of your farming operation.

At STAC in Malaysia, even non-filter feeders like jade perch\r\nand different groupers have been farmed in indoor biofloc systems, with very\r\npositive results. It is however important to avoid species which dislike murky\r\nwaters with a high solid content, like some catfish and barbs. These species\r\nsimply won’t perform as well.

Thanks to the strong aeration and self-filtering capacity of\r\nculture water, high stocking densities can be considered and it is common to\r\nstock shrimp at densities of 150 to 250 post-larvae per square metre. A safe\r\nstocking density for tilapia would be 200 to 300 fry per cubic metre. Many\r\nfarmers try to use higher stocking densities but this significantly increases\r\nthe risk of disease, compromising both the health and welfare of the animals.

Step 5: Balancing\r\ncarbon source input

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To prevent ammonia peaks (mostly originating from the\r\nnitrogen in feeds) at the start of the farming cycle, we recommend\r\njump-starting the growth and development of biofloc in your pond or raceway\r\nsystem by ensuring the sufficient availability of carbohydrates. The carbon in\r\nthese carbohydrates enables heterotrophic bacteria to multiply and synthesise\r\nammonia, thus maintaining water quality.

We advise that you select only carbon sources and feed\r\nmixtures with a carbon-to-nitrogen (C/N) ratio above 10 as this favours the\r\ngrowth of these heterotrophic bacteria. Since most fish and shrimp feeds have a\r\nC/N ratio of 9:1 or 10:1, additional inputs are needed to raise this ratio to\r\nbetween 12:1 and 15:1. Any material that contains simple sugars and breaks down\r\nquickly can be used, such as molasses, cassava, hay, sugarcane or starch.\r\nAnother solution is to reduce the protein content of the used feeds.

To prevent ammonia peaks at later stages of the production\r\nprocess, this step should be repeated, especially when using high stocking\r\ndensities in combination with large amounts of artificial feeds.

Controlling this is one of the hardest steps for\r\nsuccessfully implementing biofloc principles.

Step 6: Biofloc\r\ngrowth

With plenty of aeration, natural light (in most systems) and\r\na readily available source of carbon, your biofloc numbers should start to\r\nmultiply quickly. Depending on a variety of factors, including water\r\ntemperature, available nutrients and sunlight, plus the number of seeded\r\nbioflocs at the start of the operation, the number of flocs will increase from\r\nclose to zero to about four to five units per millilitre within a few weeks.\r\nEventually an incredible density of up to 10 billion bacteria per cubic\r\ncentimetre can be expected with, as Nyan Taw explains, “An incredible diversity\r\nof over 2,000 species,” all working hard to minimise the ammonia content in the\r\nwater column and maintain good water quality.

Monitoring the growth of these flocs can be done by using a\r\ncone-shaped beaker to collect several water samples at a depth of 15cm to 25cm,\r\npreferably in the late morning. The solid particles should be left to settle\r\nfor 20 minutes. They will stick to the sides of the cone-shaped beaker, making\r\nit easy to count them. For larger operations, the Mil Kin bacterial counter is\r\na handy tool as well.

Step 7: Monitoring\r\nand control of biofloc development

From this point on, water samples must be regularly taken to\r\nmonitor the pond water and determine the activity of the two biofloc types plus\r\ntheir respective densities. In simple terms, outdoor bioflocs consist of green\r\nalgae and brown bacteria: the algae mainly utilise sunlight for their growth,\r\nwhile the bacteria mostly consume leftover feeds, their byproducts and\r\nassociated wastes.

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Since algae initially tend to multiply faster, this means\r\nthat a pond looks green at first, turning brown over the following weeks as\r\nbacterial colonies start to dominate. With the stock growing and feeding\r\nvolumes increasing, a tipping point will be reached wherein the water will\r\nremain brown. As Nyan Taw explains: “This brown colour is more quickly reached\r\nwith tilapia as they are fed with more feeds, while it takes a bit longer with\r\nshrimp.” This colour shift is well illustrated in the colour index of Figure 4.

Step 8: Monitoring\r\nand control of water parameters and associated farm infrastructure

Once the biofloc system has turned brown, aeration must be\r\nsignificantly increased to sustain the high respiration rate. As shown in\r\nFigure 4, respiration rates at this stage can reach 6mg per litre per hour,\r\nrequiring up to six times more energy per hectare compared with the start of\r\noperations.

Any power failure at this stage can quickly result in total\r\ncrop failure due to a lack of oxygen and because in a low-oxygen environment\r\nmany heterotrophic bacteria actually start producing ammonia. It is vital for\r\nthe aeration system to stay functional at all times.

This means good maintenance and monitoring of the aerators\r\nthemselves, plus the power system that provides the energy to run this system.\r\nAs the power grid in many Asian countries is not too reliable, especially in\r\nthe rural areas where many farming operations are based, it is advisable for\r\nfarmers to invest in off-grid solutions. Several\r\nmanufacturers of paddlewheel aerators offer solar-powered\r\nversions. These are however more costly and not always that powerful. A large\r\ndiesel generator, including a second back-up generator set, might be the best\r\noption for most large-farm operations.

Regular monitoring of water-quality parameters, especially\r\ndissolved oxygen and ammonia levels, will give you a good idea if the system is\r\nworking well, or if aeration needs to be increased further.

Step 9: Monitoring\r\nand control of farm stock

Besides maintaining water quality at lower cost and without\r\nwater exchange, the second goal of a biofloc system is to improve growth rates\r\nand feeding efficiencies, thereby improving the profitability and\r\nsustainability of farming operations.

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To check how the farm is doing, regular monitoring of the\r\nperformance of the farm stock, calculating and recording growth rates, overall\r\nappearance, FCR and stock survival is required. It has been estimated that for\r\nevery unit of growth in your stock from feed, an additional 0.25 to 0.5 units\r\nof growth can come from the biofloc in your system. You should thus notice a\r\nbig jump when comparing current farm records with your previous, traditional\r\nnon-biofloc farm operations.

Step 10: Harvest and\r\nclean-up

For shrimp, a harvest of 20 to 25 tonnes per hectare can be\r\nsafely expected. If all steps have been followed, a farmer can expect increased\r\ngrowth rates and survival, thus reducing overhead costs and improving\r\nprofitability.

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Often forgotten and underestimated, proper cleaning and\r\npreparation of the pond set-up or raceway is vital after harvest time. Although\r\nit might seem appealing to reuse the culture water since it took intensive\r\neffort to build up the populations of microorganisms, this is not advisable.\r\nPathogens might have built up the culture and can pose a serious biosecurity\r\nrisk. Research has also indicated that over time, heavy metals can build up in\r\nthe culture water, which can accumulate in your stock, making it unsuitable for\r\nhuman consumption. We highly recommend cleaning up well before starting your\r\nnext profitable batch.

Source : The Fish Site