Practices of Fish farming in Biofloc culture

Biofloc fish farming in South Asia is getting popular day by day. Originated in Indonesia, this technology entered South Asian countries through some fish farmers. 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 useful product i.e. proteinaceous feed. It is the technology used in aquaculture system with limited or zero water exchange under high stocking density, strong aeration and biota formed by biofloc. The culture of biofloc will be productive in the case of culture tanks exposed to sun.


What is Biofloc technology?

Biofloc technology is a system to remove waste from water. It was previously used to treat water coming into a farm. It is done so that no diseases get transferred. This technology uses a set of bacterias which are good bacterias. These are probiotics. These probiotics kill harmful bacterias. Thus, maintaining the water quality. They also have the capabilities to convert the nitrogen in the water, into proteins.

What is Biofloc?

Biofloc is an amalgamation of different substances. Here a large number of particles clings to each other and forms a floc. There may be bacterias, protozoans, algae, organic sludge or uneaten fish feeds. The mucus secreted by the bacterias keeps all the particles together as floc. Sometimes, electrostatic forces also help them to bind together.

Biofloc system - the need

Biofloc system was developed to improve the environmental control over the aquatic animal production. In aquaculture, the strong influential factors are the feed cost (accounting to 60% of the total production cost) and most limiting factor is the water/land availability. High stocking density and rearing of aquatic animals requires wastewater treatment. Biofloc system is a wastewater treatment which has gained vital importance as an approach in aquaculture.

The principle of this technique is the generation of nitrogen cycle by maintaining higher C: N ratio through stimulating heterotrophic microbial growth, which assimilates the nitrogenous waste that can be exploited by the cultured spices as a feed. The biofloc technology is not only effective in treating the waste but also grants nutrition to the aquatic animal.

The higher C : N is maintained through the addition of carbohydrate source (molasses) and the water quality is improved through the production of high quality single cell microbial protein. In such condition, dense microorganisms develop and function both as bioreactor controlling water quality and protein food source. Immobilization of toxic nitrogen species occurs more rapidly in bioflocs because the growth rate and microbial production per unit substrate of heterotrophs are ten-times greater than that of the autotrophic nitrifying bacteria. This technology is based on the principle of flocculation within the system.

The biofloc technology has been implemented in shrimp farming due to its bottom dwelling habit and resistance to environmental changes. Studies have been conducted to assess the larval growth and reproductive performance of shrimps and Nile tilapia. An improved breeding performance was observed in shrimp reared in the biofloc system when compared to that of normal culture practices. Similarly improved larval growth performance was also noticed.

Composition and nutritional value of biofloc

Biofloc is a heterogeneous aggregate of suspended particles and 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 ranges 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.

Benefits of Biofloc culture system

• Eco-friendly culture system.
• It reduces environmental impact.
• Improves land and water use efficiency
• Limited or zero water exchange
• Higher productivity (It enhances survival rate, growth performance, 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 utilization of protein rich feed and cost of standard feed.
• It reduces the pressure on capture fisheries i.e. 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
• Start-up period required
• Alkalinity supplementation required
• Increased pollution potential from nitrate accumulation
• Inconsistent and seasonal performance for sunlight-exposed systems

The main problem of extensive fish culture in ponds is to maintain the water quality. Before biofloc way was to recycle 10% of the water frequently. But in some places, water is not present in abundance. Also, replacing the old water with new one disturbs the growth of fish. So biofloc came to solve all these difficulties.

The main agent that obstructs fish growth is ammonia. Only a fish farmer knows how cruel can ammonia be. In biofloc fish farming, we use probiotic. It utilizes the ammonia from the tank and grows in numbers by reproduction. In due course of preparing their colony, they convert the harmful ammonia and waste matter into proteins. The fishes on the tanks eat these proteins. As a result, the amount of feed given to the fishes decreases. They are already eating the proteins from the flocs. So, the feeding cost decreases by 20%-30%.

How to start your farm?

Before investing in any kind of business you need to have complete knowledge about it. Similarly, for starting biofloc fish farming you need to know about everything related to it. In the next paragraph, I will explain how to get started.

  1. Tank making
    Biofloc fish farm tanks can be either made from cement or tarpaulin. However, if you have extra money to spend. Then you can make it of stainless steel. It will be long-lasting. Whatever material you choose, you need to decide the water holding capacity. For proper growth of fish, your tank should be circular. This will hold the fishes to move in a continuous pattern without any obstruction. So fishes will grow fast. To calculate the size you need to remember this basic formula of volume of a cylinder. The depth of water in the tank should be between 3.5-4feet.
    It is V = (Π/4)*d^2*h*1000, where V=Volume of the tank in liters, d=diameter of the tank in meters h=height of the tank in meters, and Π=3.14.
  2. Water preparation in biofloc fish farming

First, you need to fill your tank with water. Then you should check its PH and Tds( Total dissolved salts). PH should be between 7.5 to 8 and TDS should be in the range of 1400-1600. If PH is low then add CaCO3. To increase TDS add raw salt. Please make sure the salt is non-iodized. Provide aeration to your tank for one day to get complete mixing. After one day, add Probiotic powder of 2 grams per 100 litre of water. Along with it mix carbon source, such as molasses of 10 grams per 100 litre of water. Then aeration should be provided. The floc takes 7 days to form. Thus, it will be ready for fish stocking.

  1. Fish stocking

Fish seeds can be bought from the market. Before stocking the fishes in the tank, you have to make it disease-free. The first step is to dip the fish seeds in Pottasium permanganate for about 30 seconds. Then the fish seeds should be kept in saline water for about 30 minutes. This will disinfect the fishes and will be ready for stocking.

  1. Maintaining water quality in biofloc fish farming

Maintaining water quality means to keep an eye on the PH and ammonia level. PH tends to decrease. If it decreases then we should add CaCo3 to increase the PH. The level should be between 7.5 to 8.

On the other hand, ammonia increase after fish is added. We provide food to the fishes for their growth. The food contains proteins. The fishes feed on these proteins and excrete waste in the form of ammonia. The uneaten food also gets converted to ammonia. So, in intensive fish culture, ammonia reaches to a higher limit, which is very harmful. To decrease ammonia, we have to add a carbon source, such as molasses. The ammonia level should be 0 ppm. The probiotics feed on these carbon sources and convert the ammonia into proteins. So the waste material of the fish gets converted to feed. In turns the cost to feed the fishes decreases.

Another important parameter is the Oxygen level. It should be around 6-8ppm. There are a lot of oxygen meters or testing kits are available in the markets. People should check the oxygen level every day. Proper pumps should be used. For a tank of 10,000-liter capacity, oxygen pump should have a flow rate of 80 liters per minute.
TDS should be around 1660. If TDS decreases, then put some raw salt (non-iodized) in your tank. If TDS increases, then replace the old water with fresh water.

How to maintain floc in biofloc fish farming?

The amount of flock you have to maintain in biofloc fish farming is 30 – 40 ml per 1000 ml. This is very essential. If floc decreases then the ammonia level will increase in your tank. If floc increases, then the water will become dense and it will be difficult for the fishes to breathe. So maintaining the floc is very important. If floc increases then replace old water with new. If floc decreases then add 25 mg probiotic along with some molasses to your tank.

How to maintain ammonia?

We need to maintain C/N ration of 10:1 in biofloc fish farming. It means the amount of carbon source required is 10 time the amount of ammonia present.

For example:
If ammonia in your tank is 1ppm, it means it is 1mg/litre
So, if your tank is of 10,000 litre and ammonia reading is 2ppm. Then it means there is a total of 20,000 mg of ammonia or 20 grams of ammonia. To diffuse this 20 grams we need (20 x 10) grams= 200 grams of carbon source.

Now the molasses that we get at cheap price has around 25% Carbon. So we need to provide (200/0.25) grams of molasses = 800 grams if ammonia level is 2 ppm. If ammonia level is 1ppm then by above calculations we need 400 grams of molasses.

Where to find all the accessories for your biofloc fish farming?

All the mentioned equiments are available in online markets. One can acquire these through local markets also. While buying the fishes, try to buy from nearby markets. Otherwise, it can be fatal for the fish lives, if transportation is too much.