Application of biofloc technology in intensive commercial tilapia farming

The application of biofloc technology (abbreviated in English as BFT) in intensive tilapia farming promotes the growth rate of farmed fish, high farming productivity, improved feed efficiency, and contributes to reducing environmental pollution in farming ponds.

The application of BFT in aquaculture is considered a new direction of biotechnology, based on the principle of supplementing carbon sources in a proportion suitable to the amount of nitrogen available in pond water to serve as food for heterotrophic microorganisms in the pond, creating conditions for this group to develop dominantly in the pond. Heterotrophic microorganisms will convert nitrogen-containing compounds in pond water into protein in biomass, thereby reusing nitrogen sources from waste dissolved in pond water and converting them into natural food biomass for farmed fish, increasing the efficiency of fish feed use.

The concept of biofloc in BFT refers to the collection of organic matter suspended in water including algae, protozoa and microorganisms - in which heterotrophic microorganisms predominate - bound together by the biological glue polyhydroxy alkanoate (PHA). The collection of bioflocs is a nutritious natural food source for tilapia raised in ponds. Therefore, the application of BFT will reduce the cost of fish feed and is considered a solution for sustainable development of aquaculture on an industrial scale.

BFT has been widely used in whiteleg shrimp farming in shrimp farms in many Southeast Asian countries. In our country, in recent years, the Aquaculture Research Institute I has deployed experimental applications of BFT in whiteleg shrimp and tilapia farming. In 2012, a group of staff from the Institute studied the application of BFT in intensive commercial tilapia farming to evaluate the possibility of applying this technology in Vietnam.

The BFT application model in intensive commercial tilapia farming consists of 2 modules, each module has 3 ponds with an average area of ​​each pond in a module of 2,000 m2 and 1,000 m2. The ponds have concrete banks, HDPE-lined bottoms, and pond water depth >1.5 m. During the farming process, the water is not changed, only the amount of water lost due to evaporation or seepage is added.

The fingerlings used for stocking are NOVIT 4 monosex tilapia, with an average size of 7.1 g/fish, raised at a density of 5 fish/m2 of pond. The fish are fed with floating pellets twice a day with equal amounts at 8am and 3pm, with a diet that meets 90% of the average satisfaction level. The fish are stopped feeding for 1 day each week to stimulate the fish to use the biofloc biomass in the pond.

The carbon source added to the pond (once a week) is molasses with a carbon content of 37.5%, used to adjust the carbon/nitrogen ratio in the pond to create a favorable environment for biofloc development and limit pond environmental pollution. The amount of biofloc bait added in the first month is 3 - 5 ppm/day; in the following months, use commercial biological products in the beneficial microorganisms with the Bacillus group to maintain stable bioflocs in the pond.

During the rearing process, operate the bottom aeration system day and night in combination with a water fan to mix the pond water evenly from the bottom layer to the surface layer and create a water flow in the pond. In the first 2 months, only run the water fan when adding molasses and biofloc bait. Then use both bottom aeration and water fans continuously until harvest to maintain oxygen and ensure biofloc is suspended in the water.

After 177 days of intensive farming of commercial tilapia using BFT, the model achieved the following results: The average weight of farmed fish reached 624.2 g/fish, the average growth rate was 3.53 g/fish/day, the time for fish to reach an average size of 500 g/fish was 18 days earlier than farming without BFT; The average feed conversion ratio was 1.35 - a decrease of 20.6% compared to farming without BFT; The survival rate of farmed fish was 81.6 - 85.7%; The yield was 23.6 tons/ha/6-month farming crop; The protein utilization efficiency was 2.65 g; The rate of feed protein converted into biomass was 50.48% - an increase of 10.41% compared to farming without BFT. The pond environment is maintained clean because this technology can convert up to 51% of the nitrogen input into the farming system into biomass.

Regarding the economic efficiency of the model, the figures show: Total investment for 1 hectare of intensive commercial tilapia farming with BFT application is 526,662 million VND; Total revenue is 627,600 million VND; Net profit is 100,938 million VND; Profit/capital ratio is 19.17% for a 6-month farming cycle; Cost price of 1 kg of commercial fish is 23,316 VND, average selling price is 26,500 VND/kg, farmers earn 3,184 VND/kg.

In summary, the application of BFT in intensive commercial tilapia farming has achieved remarkable results, demonstrated by promoting the growth rate of farmed fish, achieving high farming productivity, improving feed efficiency, and contributing to reducing environmental pollution in the pond. However, according to the research team, this model is suitable for farming facilities that are capable of investing in infrastructure and technology.

According to Bannhanong