Biofloc Culture Notes for IBPS AFO & NABARD
What is Biofloc Culture?
It is an innovative and cost-effective technology in which toxic materials to the fish and shellfish such as Nitrate, Nitrite, and Ammonia can be converted to a useful product, ie., proteinaceous feed. It is the technology used in aquaculture systems 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 the nitrogen cycle by maintaining a higher C:N ratio through stimulating heterotrophic microbial growth, which assimilates the nitrogenous waste that can be exploited by cultured spices as feed. The biofloc technology is not only effective in treating waste but also grants nutrition to aquatic animals.
The higher C: N is maintained through the addition of a carbohydrate source (molasses) and the water quality is improved through the production of high-quality single-cell microbial protein. In such conditions, dense microorganisms develop and function both as bioreactors controlling water quality and protein food sources. Immobilization of toxic nitrogen species occurs more rapidly in bio flocs because the growth rate and microbial production per unit substrate of heterotrophs are ten times greater than that of the autotrophic nitrifying bacteria.
Composition and nutritional value of biofloc
Biofloc is a heterogeneous aggregate of suspended particles and a variety of microorganisms associated with extracellular polymeric substances. It is composed of microorganisms such as bacteria, algae, fungi, invertebrates, detritus, etc. It is a protein-rich live feed formed as a result of the conversion of unused feed and excreta into a natural food in a culture system on exposure to sunlight. Each floc is held together in a loose matrix of mucus that is secreted by bacteria and bound by filamentous microorganisms or electrostatic attraction. Large flocs can be seen with the naked eye, but most of them are microscopic. Floc size ranges from 50 – 200 microns.
A good nutritional value is found in biofloc. The dry weight protein ranges from 25 – 50 percent, and the fat ranges 0.5 – 15 percent. It is a good source of vitamins and minerals, particularly phosphorous.
Benefits of Biofloc culture system
- Eco-friendly culture system.
- Improves land and water use efficiency
- Limited or zero water exchange
- Higher productivity (It enhances survival rate, growth performance, and 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 the utilization of protein-rich feed and the cost of standard feed.
- It reduces the pressure on capture fisheries ie., the 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.
- A start-up period is required.
- Alkalinity supplementation is required.
- Increased pollution potential from nitrate accumulation.
- Inconsistent and seasonal performance for sunlight-exposed systems.
Species suitable for Biofloc Culture
Biofloc system works best with species that are able to derive some nutritional benefits from the direct consumption of floc. Biofloc system is most suitable for species that can tolerate high solids concentration in water and are generally tolerant of poor water quality. Some of the species that are suitable for BFT are:
Air-breathing fish: like Singhi (Heteropneustes fossilis), Magur (Clarias batrachus), Pabda (Ompok pabda), Anabas/Koi (Anabas testudineus), Pangasius (Pangasianodan hypothalamus).
Non-air-breathing fishes: like Common Carp (Cyprinus carpio), Rohu (Labeo rohita), Tilapia (Oreochromis niloticus), Milkfish
(Chanos chanos).
Shellfish: like Vannamei (Litopenaeus vannamei) and Tiger Shrimp (Penaeus monodon).
In conclusion, Biofloc Culture is a promising technology that has gained popularity in the aquaculture industry in recent years. It offers many benefits such as eco-friendliness, improved land and water use efficiency, higher productivity, higher biosecurity, cost-effective feed production, and reduced pressure on capture fisheries. However, it also has some disadvantages such as increased energy requirement, reduced response time, a start-up period, the need for alkalinity supplementation, increased pollution potential, and inconsistent performance in sunlight-exposed systems. This technology is best suited for species that are able to derive some nutritional benefits from the direct consumption of floc and can tolerate high solids concentration in water. Some of the species suitable for this technology include air-breathing fish like Singhi and Magur, non-air-breathing fish like Common Carp and Tilapia, and shellfish like Vannamei and Tiger Shrimp.
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