Biofloc Fish Farming – A Novel Aquaculture Technology

A goal of aquaculture, is to produce a healthy fish, to assure the maximum profit. Diseases and unregulated water quality management in the culture systems interferes with this. Application of antibiotics, for the treatment of bacterial diseases, was encouraged in the past. However, aquaculture depends on antibiotics, and is now criticized.

In the traditional aquaculture systems anaerobic conditions were created due to a huge fraction of organic matter settling down to the bottom of the pond thereby resulting in the production of toxic compounds like ammonium and nitrites, both of which are deleterious to fish. The resultant low rate of bio-recycling led to an inability to increase intensification and lower feed utilization.Thus, strategies aimed to overcome these challenges are required.

What is Biofloc Technology?

Biofloc technology (BFT) is considered a “blue revolution” in aquaculture. It is an environmentally friendly aquaculture technique that has been introduced and developed in order to increase the regulation of the environment in aqua farming. It is a technology in which the materials which are harmful and poisonous to the fish or shrimp are transformed into some protein food. This is basically used in aqua farming when the density of stocking is high with very less exchange of water. This method would be run productively when the tanks used are kept in direct sunlight.

Fish and shrimp are grown in an intensive way with zero or minimum water exchange. In addition, continuous water movement is required to induce the biofloc formation. Nutrients in water will contribute to a heterotrophic microbial community formation and stabilization.The culture of biofloc will be productive in the case of culture tanks exposed to sun.The consumption of biofloc by shrimp or fish has demonstrated numerous benefits such as improvement of growth rate, decrease of Feed Conversion Ratio and associated costs in feed.

Why to choose Biofloc Technology?

The limitations of traditional aquaculture that led to evolution of biofloc technology mainly includes the following influential factors

  • water/ land availability 
  • Feed cost (accounting to 60% of the total production cost) 

If the stocking has to take place at high density, then the wastewater should be treated on a higher basis. Biofloc system is the one which has been brought into existence and was given more importance only in order to treat the wastewater in aqua farming.

What is the purpose of Biofloc Technology?

In the Biofloc system, the nutrients and the wastes that occur from nitrogen are recycled. The recycling is done by keeping the ratio of nitrogen and carbon dioxide at high levels in the water. These are maintained at high levels for the stimulation of bacteria which are heterotrophic. The growth of bacteria will be enhanced when the sources of carbon dioxide like cellulose or molasses are kept in the pond with continuous circulation of air. By the maintenance of the ratio of carbon and nitrogen by the addition of sources of carbon, the production of the microbial protein with high quality is done. Through Biofloc systems, the water quality increases. Along with the quality of water, there would be the availability of a very good nutrition source to the fish or shrimp, which helps them in their healthy growth and increases their resistance to diseases. This method can be implemented after checking the pH levels of water along with temperature, levels of oxygen which are dissolved etc.

The main motto of this system is to generate the cycle of nitrogen by having a Carbon and nitrogen ratio at a higher rate by encouraging the growth of microbes which is heterotrophic. This absorbs the wastes of nitrogen, which can be damaged by the cultured species as they take it as a food.

When the ratio of carbon and nitrogen are maintained at high rates, then the microorganisms will be developed in more numbers and work in controlling the quality of water and the food source. The fixation of nitrogen species which are poisonous will be done quickly in the Biofloc systems. This is because the growth of microbes will be ten times more than that of the bacteria which are autotrophic.

This system is used in the production of shrimps as it dwells at the bottom of the water and is very adaptable to the changes in the environment. Compared to other traditional practices, Biofloc proved to improve the production of shrimps.

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 and detritus, etc. It is a protein-rich live feed formed as a result of 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 range from 50 – 200 microns.

A good nutritional value is found in biofloc. The dry weight protein ranges from 25 – 50 percent, fat ranges 0.5 – 15 percent. It is a good source of vitamins and minerals, particularly phosphorous. It also has an effect similar to probiotics. The dried biofloc is proposed as an ingredient to replace the fishmeal or soybean in the feed. The nutritional quality is good; however, only limited qualities are available. Furthermore, the cost-effectiveness of producing and drying biofloc solids at a commercial scale is a challenge.

Pros and cons of Biofloc Technology Aquaculture System:

Pros :

  • Biofloc systems are environment-friendly as they have no bad effects on the environment.
  • The usage of water and the area would be improved.
  • The exchange of water will be less.
  • It improved the survival rate of the fish, thereby increasing the production.
  • It follows the procedures which are designed to save the species from harmful biological substances.
  • Water will be saved from pollution and there would be no pathogens growing in the water.
  • The production of feed will take less cost.
  • The feed which is rich in proteins can be used less which thereby decreases the feed cost.

cons:

  • For the purpose of mixing and the circulation of air, there would be more levels of energy required.
  • Because of the increase in the respiration rates in water, the rate of response will decrease.
  • It takes some time to start the process and its execution.
  • The alkaline content should be supplemented.
  • Due to the gathering of nitrate content, there would be an increase in the pollution. For the systems which are exposed to sunlight, the results might not be consistent.