One type of fish that can be cultivated with a biofloc system is catfish. This catfish is a type of carnivorous fish that requires feed with high protein content for its growth. The protein content of the feed is not all absorbed in the body of the catfish, only about 20-30% can be absorbed, the rest accumulates in water both in the form of feces and urine.
Organisms that live in water in the metabolic process generally produce ammonia as a result of its excretion. High protein from uneaten feed residues and metabolite decomposition results will produce the same by-product, ammonia in the form of Total Ammonia Nitrogen.
Waste from aquaculture in the form of ammonia can reduce the level of water quality and this waste is toxic and can kill the fish being raised. Ammonia produced from fish farming will be a limiting factor in the success of fish farming.
Fish farming activities will be successful if ammonia control can be done with good management. The usual method is to change water regularly. However, this periodic water change method will require large amounts of water and the used water discharged can become waste that can pollute the environment.
One solution that can be done and an environmentally friendly solution is the application of biofloc system fish farming. Biofloc is a system that manipulates microbial activity as a way to control water quality by transforming ammonium into microbial proteins that can reduce residues in the remaining feed.
Bioflocs are usually particles stirred by aeration and circulation systems consisting of a collection of autotrophs, heterotrophs, and other living organisms such as bacteria, phytoplankton, fungi, ciliates, nematodes and detritus.
The concept and workings of bioflocs are very simple, namely nitrogenous waste that has the potential to become toxic is converted into bacterial proteins that can be utilized by fish. Fish can utilize dual proteins derived from feed and microbes. This microbial protein is actually a recycling of feed protein that is utilized.
The basic principle of this biofloc fish farming system is to convert organic compounds and inorganic compounds containing carbon, hydrogen, oxygen and nitrogren compounds into sludge mass in the form of bioflocs by using floc-forming bacteria which are polyhydroxyl alkanoate biopolymers as biofloc bonds.
This biofloc system will require vigorous aeration and stirring of the water in the fish pond to continuously maintain the suspension of organic waste for digestion by the bacteria. Aerobic heterotrophic bacteria colonize the organic waste particles and absorb nitrogen, phosphorus and other nutrients in the water.
The process improves the water quality of the fish pond and recirculates the effluent as the detritus is bacterially enriched. Floc particles are agglomerated with polysaccharides produced by bacteria. Suspended materials are adsorbed on top of the bacterial floc which is hydrolyzed by bacterial extracellular enzymes.
The biofloc system in fish ponds is a direct biofilter as there is no external filtration system and little or no solids removal is required.