Biofloc technology is gaining popularity among aquaculture farmers as a sustainable way to raise fish and shrimp. This system allows you to achieve high densities of shrimp in smaller tanks by converting toxic ammonia into a protein-rich feed source. But how many shrimp can realistically be stocked and grown in a 10,000 litre biofloc tank? In this post, I’ll provide some calculations and recommendations based on common biofloc shrimp farming practices.
What is Biofloc Technology?
Biofloc systems work by promoting the growth of beneficial bacteria which convert toxic ammonia into nitrates. These nitrates fuel the growth of oxygen-producing algae and zooplankton, which the shrimp then consume as a natural food source. The continuously multiplying biomass of suspended solids in a biofloc tank is referred to as “bioflocs”.
Some key advantages of biofloc systems:
- Remove need for water exchange, recycling water and minimizing waste
- Reduce need for expensive commercial feeds
- Improve growth rates and FCR (food conversion ratio)
- Improve water qualty through rapid ammonia assimilation
- High stocking densities possible in small tanks
Calculating Shrimp Density in a Biofloc Tank
Stocking density is typically measured as the number of shrimp per square meter of surface area. This takes into account the total volume of the tank and the surface area available for the shrimp to access oxygen.
For a 10,000 litre circular tank with a diameter of 5 meters, the surface area would be around 196 square meters
Based on research and trials optimal stocking densities for biofloc systems range between 300-500 shrimp per square meter.
So for a 10,000 litre tank of 19.6 square meters, you could stock approximately:
- 5,900 shrimp at 300/m2 density
- 9,800 shrimp at 500/m2 density
However, these are theoretical maximums under ideal conditions. In reality, the density should be tailored to each specific farm based on:
- Water quality – biofloc buffering capacity
- Supplemental aeration and circulation
- Shrimp species and culture goals
- Feeding rate and biofloc production
- Farm management level and experience
Most experts recommend starting with lower densities around 300-350/m2 for new biofloc systems, and slowly increasing to 450-500/m2 once the biofloc and shrimp are well established.
Densities above 500/m2 are not recommended as this could compromise growth rates and water quality. Below 300/m2 may result in underutilization of the tank capacity.
Other Factors Impacting Stocking Density
While surface area provides a useful guideline, there are other factors that influence how densely you can stock shrimp in a biofloc system:
1. Oxygenation and aeration
Maintaining dissolved oxygen is crucial, especially at higher densities. Strong aeration is needed 24 hours per day to maintain oxygen above 5 ppm. Using air blowers, air stones, paddwheel aerators, and vigorous mechanical circulation can provide sufficient oxygenation.
2. Species of Shrimp
Some species tolerate crowding better than others. The commonly farmed Pacific whiteleg shrimp and Indian white shrimp are good biofloc species options. Larger shrimp may require lower densities.
3. Water Exchange
Minimal or no water exchange is ideal in biofloc systems. However, you may need periodic small exchanges at higher densities to stabilize water quality. This depends on biofloc balance and supplemental aeration provided.
4. Tank Design and Shape
Rectangular concrete tanks allow for better circulation and solid removal compared to circular tanks. Tank shape impacts how evenly biofloc is distributed.
5. Climate Conditions
In tropical climates, higher densities are possible. In cooler climates, densities should be reduced to account for lower metabolism and feed consumption of shrimp.
6. Supplemental Feeding
While bioflocs provide natural food, you still need quality supplemental feed to balance nutrition. Feed frequently throughout day to maintain water quality.
Management Tips for High-Density Biofloc Shrimp Farming
Here are some key tips to successfully manage a high density biofloc shrimp system:
- Start with conservative stocking, increasing gradually over 2-4 months
- Provide vigorous 24/7 aeration – at least 10-20 air changes per hour
- Use high-protein feeds with 35-40% protein content
- Monitor and maintain ammonia, nitrite, nitrate, pH and alkalinity daily
- Test settleable solids; harvest biofloc if solids concentration exceeds 400-500 ml/L
- Observe shrimp behavior closely for signs of stress
- Be prepared to reduce feeding and densities if needed to stabilize system
- Change feeds gradually to avoid water quality fluctuations
- Use probiotics and supplements to enhance biofloc development
- Ensure tanks are thoroughly cleaned between cycles
To summarize, a 10,000 litre biofloc tank with 19.6 m2 surface area could potentially accommodate between 5,900-9,800 shrimp at stocking densities of 300-500/m2. However, it is best to take a conservative approach and build up density gradually in your system based on supplemental aeration, biofloc development, and overall water quality management. Targeting an initial stocking around 300-350/m2 is recommended, increasing slowly to 450-500/m2 at maximum. With close monitoring and care, high-density biofloc shrimp farming can produce impressive yields. But densities should not compromise the health and growth of the shrimp.