China Aquatic Channel original exclusive report, in recent years, we talk about a technology is the application of biological flocculent in South American white shrimp farming, in fact, this technology in catfish farming also has a lot of classic cases, especially in Southeast Asia, the technology has been favored by some family farms, there are reports showing that the highest unit yield of catfish cultured with biological flocculent technology with circulating water technology can reach 250 kg / m3, generally can reach 30-40 kg / m3.
Biological flocculent refers to the granular matter formed by regulating the nutritional structure in the water body, promoting the proliferation of heterotrophic bacteria in the water body, and combining bacteria, protozoa, algae, organic matter and inorganic substances in the water body through biological flocculation. In the process of breeding, by adjusting the carbon-nitrogen ratio in the water body, promoting the large number of heterotrophic bacteria in the breeding system, and then forming a variety of micro and small organisms of flocculent particles, and absorbing nitrogen in the water body through assimilation, it is converted into a protein source that can be reused by farmed animals, effectively reducing the harmful nitrogen content such as ammonia nitrogen and nitrogen nitrite in the farmed water body, greatly improving the utilization rate of feed protein, building a benign pond ecological nutrition cycle, and promoting the efficiency, conservation, environmental protection and health of the aquaculture industry.
However, due to the strong respiration effect of heterotrophic bacteria during the proliferation of heterotrophic bacteria, the dissolved oxygen consumption of water bodies under the breeding conditions of biological flocculent technology is significantly higher than that of traditional breeding conditions, so it is necessary to continuously maintain the oxygenation of the aquaculture water body, which also brings a higher cost of oxygenation, which farmers need to pay attention to.
Researchers in Indonesia did experiments in 2014, in 2 × 1.5 × 0.7 meters of size of the pond stocked 5000 catfish (average weight 2.5 grams) of catfish, the density reached 2380 fish / cubic meter, using bioflocation technology combined with circulating water technology, and finally harvested an average of 1 cubic of water body 250 kg catfish, the ratio of 0.9-1.
The background of the development of this technology is mainly to solve the problems of limited freshwater resources, environmental pollution, and low resource efficiency, while changing the dirty impression of catfish in consumers' minds. Such a high yield also benefits from the catfish's ultra-high environmental tolerance and disease resistance, making it very suitable for high-density farming, and from the current production of catfish cultured in family farms in Southeast Asia using biological flocs, the unit yield can generally reach 30-50 kg/m3.
Another experiment compared the advantages and disadvantages of farming leather-bearded catfish in earthen ponds and biological flocculent techniques. The seedling density of the soil pond was 1.5 fish/m2, which was 1000 fish/mu, and the density of the biological flocculture system was 12.6 fish/m2, 8405 fish/mu, and the average seedling size was 47 g/tail. After 210 days of rearing, the average weight of the fish in the outer pond is 630 g/tail, and the bio-flocculture system is 542 g/tail. That is to say, the catfish cultured in the outer pond is larger in size, and the fish cultured in biological flocs is smaller in size. Despite differences in specifications, bioflocation systems have higher yields per unit of 7.7 kg/m3 due to high stocking densities, compared to 1.5 kg/m3 in outer ponds. Compared to hydrostatic ponds, biofloc culture systems reduce the incidence of catfish mud odor and thus improve meat quality. In addition, bioflocs contain a wealth of natural probiotics that resist Vibrio and parasitic infections.
In ponds, algae absorption of ammonia nitrogen is dominant, with almost no nitrification, while in the biofuff system, the absorption and nitrification of algae maintain a low ammonia nitrogen concentration in the water, so the cultivation of biological flocculents is the most critical technology. Adding molasses is a more cost-effective way to increase the nutrition of probiotics, thereby improving the water purification ability of probiotics. At the same time, the nutritional value of the biological flocculant is improved, thereby improving the growth rate of catfish and reducing the feed coefficient. Usually, farmers first add 1.5 kg of fishmeal, 1.5 kg of grain, 250 mg/L molasses and 5 mg/L probiotics (Bacillus) in 30 liters of water, ferment for 24 hours, and then pour the fermented probiotics into the breeding pond, through fermentation can enrich the biofloc content and activity.
In the process of using biological flocculent technology to cultivate catfish, it is also necessary to pay attention to some key factors, first of all, to select excellent fry to improve production efficiency. Secondly, it is necessary to choose a wide range of feeds, different feeds or baits have a direct impact on the formation of biological flocs, so it is necessary to adjust the feed and feeding strategy according to the situation. Due to the high cost of feed now, farmers can consider using alternative raw materials or their own feed for breeding. Third, we must make a good breeding plan. The accuracy of the feeding plan will affect the harvest, not the higher the yield, the better, according to the market situation, the harvest specifications are indeed the breeding density to ensure the maximum output and benefits of the unit. Finally, it is necessary to pay attention to the application of probiotics and regular small amounts of water change to keep the biological floc in good condition.