Biofloc technology is a new revolution in aquaculture and is a beneficial approach to sustain our ecosystem. Due to climate change, the new technology helps to control the pollution thus give a good business sight. Biofloc technology has a different concept from Recirculating aquaculture system (RAS) methods. In RAS, a biofilter is used to remove the compounds and reduce ammonia toxicity.
Figure 1. The indoor biofloc system here in RAS Aquaculture
The usage of formulated feed as the source of nutrients and protein has been applying worldwide. Uneaten or leftover feed are some of the challenges faced by the farm operator which are costly. Biofloc technology is well known for its ability to reduce feed conversion ratio (FCR) at 1 to 1.5. The amount of feed can be reduce because of increasing culture feasibility or food source from the biofloc. Therefore, the technology helps to improve the understanding of feeding rate or intake rate which is different according to body weight of shrimps to avoid overfeeding. Here in RAS Aquaculture, the FCR can be reduced around 1.3 to 1.4 at some time between the culture period. FCR is the amount of feed we used to get 1 kilogram of body weight and usually feed can be up to 60% of the operational cost. Thus, reducing FCR is a good indicator for a feeding strategy to reduce cost operation.
In aquaculture, maintenance of water quality is a crucial aspect to focus on. Biofloc technology helps to control water quality which is essential for the success of the growing cycles. Daily monitoring of water parameters will ensure the quality of biofloc is at its optimum. Water quality parameter such as ammonia which is one of the most toxic inorganic compounds that are produced in water can only be removed by bacterial activity through conversion into a less toxic compound (nitrate). Dissolved oxygen and solid also should be measured daily to make sure that if there any changes with the water quality, fast actions can be taken to avoid further losses. Applying biofloc technology also has minimal to zero water exchange. Farm operators that have earthen ponds or tanks located near to the sea have the advantage to exchange the water easily. But, the new technology has benefited the farm operator with indoor farming or without excess to seawater.
Figure 2. Daily monitoring of water quality using commercial test kits and Imhoff cone is very important in biofloc system
Biofloc technology helps in disease control and management in the shrimp culture industry. Shrimp are very vulnerable to diseases and can easily infect one another. However, the mechanisms with probiotic which contains bacteria like Bacillus sp. will affect the shrimp performance. The probiotic can increase the disease resistance of the shrimp. Beneficial effects are observed by the addition of probiotics by showing a strong immune response of the shrimp toward the pathogens. Therefore, if a pathogen like Vibrio sp. present in the water, the shrimp immunity would be able to fight against it.
Microorganisms play a major role in biofloc technology. Phytoplankton, heterotrophic, and nitrifying bacteria have the most important role in biofloc while fungi, ciliate, protozoa, rotifer, copepod, and nematode complement the biofloc community by participating in the food web that includes the cultured animal too. There are few types of bacteria present in biofloc. The heterotrophic bacteria consume organic compounds as a carbon source and convert them into bacterial biomass. Therefore, this community minimizes ammonia accumulation in the water. Photoautotrophs make their food by transforming sunlight into photosynthesis while autotrophic bacteria make their food from inorganic molecules like ammonia and nitrate. There is also a chemoautotrophic bacterial community like nitrifying bacteria that obtain energy through the oxidation of toxic nitrogen compounds. The shrimp grow best under the presence of a diverse community, called the mixotrophic.
A fully indoor farm near the capital has high potential's advantage. The business is directly passed to the end consumer and thus has a short supply chain. The white-leg shrimp (Litopenaeus vannamei) has been for 82 DOC for the last batch. The shrimp can be sold as a live product when they are ready to be harvested and actually has a higher price compared to frozen product. The freshness and quality are ensured to achieve consumer satisfaction.
However, only certain animals can live in biofloc water so it is very important to properly choose the species that need to be culture. Here, Litopenaeus vannamei or white leg shrimp is cultured because of their special characteristics compared to other species. Vannamei shrimp is an omnivore, which means they eat both animals and plants. As biofloc water consists of algae, protozoa, plankton and bacteria, they are suitable for omnivore animals. Next, the adaptability of vannamei shrimp to high turbidity. Biofloc water is brown and has high turbidity which is caused by the solids from the uneaten feed and feces and the floc itself. So it is an important characteristic to the animal to adapt. Lastly is the tolerance to low oxygen. The microbial community inside the water also takes up oxygen for respiration and although the algae produce oxygen through photosynthesis, it is still not enough. Therefore, the shrimp need to have a tolerance to low dissolved oxygen which is around 5 ppm. Another animal such as the catfish also can tolerate low oxygen in biofloc which is even lower at 3 ppm.
Figure 3. Litopenaeus vannamei or white leg shrimp
Biofloc systems can reduce disease outbreak. Disease outbreaks usually happen because of the weak host, bad environment, low water quality and presence of the pathogen. To avoid disease outbreaks, usually, the farm operator should act accordingly to the main factors. In biofloc, the ability of wastes to be converted into less toxic compounds will ensure a stable environment for the shrimp. A variety of beneficial microorganisms will help to eliminate the presence of the bad pathogen. The shrimp or post-larvae that need to be culture must be originally free from disease or specific pathogen-free (SPF) products which can be obtained from the certified hatchery.
Figure 4. These post-larvae were acclimatized in the nursery tank are specific pathogen-free (SPF)
The basic process for setting up a biofloc system involves the assimilation, nitrification, and oxidation process. First of all, an adequate amount of feed or urea, and sugar, molasses or flour and a bit of probiotic to enhance the bacterial community is needed to form the floc. Feed or urea is the source of nitrogen for the shrimp, while sugar, molasses, or flour is the source of carbon for microbial activity. It is not necessary to mix everything up but it Is important to understand the combination is actually to make carbon to nitrogen ratio. Usually, to set up your floc formation, we use a minimum carbon to nitrogen ratio of 20:1 which is the easiest part. The difficult part is when to stop your floc formation and the monitoring throughout your culture cycle. The floc formation stage can be observed when normal clear seawater becomes brownish. Next, a microbial community inside the biofloc water needs to be observed frequently. This is crucial before you stock your shrimp for a nursery or grow out. A variety of microbes means that the biofloc water is ready to use. Bio solid generation through Imhoff cone measurement and total suspended solid should also be observed closely.
Shrimp need protein from the formulated feed but the formation of floc in the system can act as the extra feed to the shrimp. All the shrimp waste from the uneaten feed or feces will be recycled back into the water by the microbial community inside the water which is also called the in-situ conversion. However, the biofloc cannot be served as main feed although the shrimp might survive the growth and will be lower and not achieve the desired size during the harvest period. The normal size for L. vannamei in the harvesting period is between 20 to 25 g after culturing for 120 days. Longer culturing time might have bigger size shrimp but the cost might increase too.
Biofloc technology is a new environmental friendly concepts in aquaculture. It is an efficient alternative system as the nutrients can be continuously recycled. The sustainable approach is based on growth of microbial communities with zero to minimal water exchange. The technology may bring higher profit if its nearer to consumers and the advantages certainly should be explored more.