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Flow-Through and Recirculatory Water Systems for Fish Tanks

Enhance fish farming efficiency with sustainable water systems, reducing resource wastage and ensuring robust fish growth.

The recirculatory aquaculture system (RAS) technology is an innovative method used in fish farming that optimizes water usage by continuously recycling and purifying water within a closed-loop system. In RAS, water from the fish tanks is filtered to remove waste products and then recirculated back into the tanks, reducing the need for large volumes of fresh water. This technology enables higher fish stocking densities, leading to increased productivity and efficiency compared to traditional aquaculture methods. RAS also allows for better control of water quality parameters such as oxygen levels, temperature, and pH, resulting in healthier fish and reduced environmental impact. Overall, RAS represents a sustainable and environmentally friendly approach to fish farming that maximizes resource utilization and minimizes waste.


This technology is TAAT1 validated.


Scaling readiness: idea maturity 7/9; level of use 8/9

Cost: $$$ 22000 USD

Pumping and piping for recirculation system (130 m3)

44000 USD

Recirculation System (130 m3) treatment

1.5—5 USD

Settling of square meter pond construction


Open source / open access


  • Limited land and water resources for traditional fish farming methods: Traditional fish farming often requires large expanses of land for ponds or access to natural water bodies. However, in many regions, land suitable for aquaculture is limited, and water resources may be scarce or already heavily utilized for other purposes such as agriculture or domestic use. This limitation restricts the scalability and sustainability of traditional fish farming practices.
  • Challenges in maintaining water quality and oxygen levels for successful fish farming: Water quality is crucial for the health and growth of fish in aquaculture systems. However, in traditional methods, maintaining optimal water quality can be challenging, especially in densely stocked ponds or areas with limited water exchange. Poor water quality can lead to stress, disease outbreaks, and reduced growth rates in fish populations, ultimately affecting farm productivity and profitability.
  • Need for effective waste management and control of pollutants in aquaculture systems: Aquaculture systems generate various types of waste, including uneaten feed, feces, and metabolic by-products from fish. If not managed properly, these wastes can accumulate in the water, degrade water quality, and create favorable conditions for the growth of harmful bacteria and algae. Effective waste management strategies are essential to minimize environmental impact and maintain a healthy aquatic ecosystem.
  • Dependence on reliable water sources and electricity infrastructure for flow-through systems: Flow-through aquaculture systems rely on continuous water exchange to maintain water quality and oxygen levels. As a result, they are highly dependent on reliable access to clean water sources, such as rivers or lakes, and electricity infrastructure to power water pumps and filtration equipment. In regions with unreliable water or electricity supply, the feasibility of implementing flow-through systems may be limited.
  • Importance of proper tank design and equipment selection for efficient water flow and filtration: The design of aquaculture tanks and selection of equipment play a critical role in the efficiency and effectiveness of water flow and filtration processes. Tanks must be designed to facilitate proper water circulation, oxygenation, and waste removal, while filtration equipment must be appropriately sized and configured to handle the volume and type of waste generated. Poor tank design or inadequate equipment selection can lead to inefficient water management, increased operational costs, and compromised fish health and productivity.
  • Challenges in regulating water temperature, oxygen levels, and pH in recirculating systems: Recirculating aquaculture systems require precise control of water parameters such as temperature, oxygen levels, and pH to maintain optimal growing conditions for fish. However, fluctuations in these parameters can occur due to factors such as environmental conditions, system dynamics, and biological processes. Achieving and maintaining proper water quality parameters in recirculating systems can be challenging and requires careful monitoring, adjustment, and management strategies to ensure fish health and productivity.


  • Efficient Use of Limited Resources: The technology allows for the maximum utilization of limited land and water resources by enabling higher density fish culture. This means that a greater number of fish can be raised in a smaller area compared to traditional methods, making it more efficient and sustainable.
  • Maintenance of Peak Water Quality: Despite dense stocking rates, the system ensures peak water quality conditions within the tanks. Through continuous filtration and purification processes, suspended matter and waste products are removed from the water, preventing the buildup of harmful substances and maintaining a healthy environment for the fish.
  • Continuous Water Filtration and Purification: One of the key features of the technology is its ability to continuously filter and purify water. This not only keeps the tank clean but also ensures that the water remains free from contaminants, pathogens, and excess nutrients that could negatively impact fish health.
  • Conversion of Waste Products: Waste products generated by the fish are either removed from the system or converted into non-toxic substances that can be used for cultivating crops. This adds an additional layer of sustainability to the system by minimizing waste and potentially creating value from by-products.
  • Flexibility in Location Choice: Depending on the availability of water and electricity, the technology offers flexibility in choosing the location for setting up the aquaculture system. It can be implemented in areas with reliable water sources but limited access to electricity, or vice versa, allowing for adaptation to local conditions.
  • Adaptability to Various Tank Designs: The technology can be adapted to different tank materials and designs, including circular and rectangular shapes. This versatility allows for customization based on specific requirements such as space availability, cost considerations, and environmental conditions.
  • Integration of Filtration and Conditioning Units: In recirculating systems, filtration and conditioning units are integrated into the setup to optimize water quality. These units help regulate parameters such as water temperature, oxygen levels, and nutrient concentrations, ensuring optimal conditions for fish growth and health.
  • Regulation of Water Parameters: The system includes mechanisms for regulating key water parameters such as temperature, oxygen levels, and pH. This ensures that the aquatic environment remains stable and conducive to fish growth, minimizing stress and promoting overall well-being.

Key points to design your business plan

Maximize fish production, minimize expenses, and ensure top-tier product quality through RAS technology. Enhance operational efficiency, mitigate environmental impact, and stimulate economic progress within your locality. Position yourself as a pioneer in sustainable aquaculture methods and innovation.

Regarding expenses, take into account the estimated costs for recirculation pumping and piping, approximately USD 22,000, and mechanical, physical, biological, and chemical treatment, around USD 44,000 for a 130 m3 tank. Additionally, factor in water supply and treatment expenses, influenced by drainage specifics. Contractor fees for constructing a settling pond typically range from USD 1.5 to 5 per square meter, depending on soil type and lining materials.

Given the widespread availability of this technology, consider delivery expenses to the project site and account for any import-related fees.

Collaboration with agricultural development institutions and agro-dealers can facilitate effective implementation.

Furthermore, explore the incorporation of complementary technologies like All Male Tilapia Fingerlings with Greater Yield and Uniformity and Fast Growing and Hybrid African Catfish to maximize overall efficiency.


Positive or neutral impact

Adults 18 and over
Positive high
The poor
Positive low
Under 18
Positive medium
Positive medium

Positive or neutral impact

Climate adaptability
It adapts really well
Adaptability for farmers
It helps a lot
It helps them grow and thrive
Carbon footprint
It reduces emissions a little
It makes a big difference
Soil quality
It makes the soil healthier and more fertile
Water usage
It uses a lot less water

Countries with a green colour
Tested & adopted
Countries with a bright green colour
Countries with a yellow colour
Egypt Equatorial Guinea Ethiopia Algeria Angola Benin Botswana Burundi Burkina Faso Democratic Republic of the Congo Djibouti Côte d’Ivoire Eritrea Gabon Gambia Ghana Guinea Guinea-Bissau Cameroon Kenya Libya Liberia Madagascar Mali Malawi Morocco Mauritania Mozambique Namibia Niger Nigeria Republic of the Congo Rwanda Zambia Senegal Sierra Leone Zimbabwe Somalia South Sudan Sudan South Africa Eswatini Tanzania Togo Tunisia Chad Uganda Western Sahara Central African Republic Lesotho
Countries where the technology has been tested and adopted
Country Tested Adopted
Benin Not tested Adopted
Botswana Not tested Adopted
Burundi Not tested Adopted
Cameroon Not tested Adopted
Côte d’Ivoire Not tested Adopted
Democratic Republic of the Congo Not tested Adopted
Djibouti Not tested Adopted
Equatorial Guinea Not tested Adopted
Ethiopia Not tested Adopted
Kenya Not tested Adopted
Madagascar Not tested Adopted
Malawi Not tested Adopted
Nigeria Not tested Adopted
Rwanda Not tested Adopted
Senegal Not tested Adopted
Sierra Leone Not tested Adopted
South Sudan Not tested Adopted
Sudan Not tested Adopted
Tanzania Not tested Adopted
Uganda Not tested Adopted
Zambia Not tested Adopted
Zimbabwe Not tested Adopted

This technology can be used in the colored agro-ecological zones. Any zones shown in white are not suitable for this technology.

Agro-ecological zones where this technology can be used
AEZ Subtropic - warm Subtropic - cool Tropic - warm Tropic - cool

Source: HarvestChoice/IFPRI 2009

The United Nations Sustainable Development Goals that are applicable to this technology.

Sustainable Development Goal 2: zero hunger
Goal 2: zero hunger
Sustainable Development Goal 6: clean water and sanitation
Goal 6: clean water and sanitation
Sustainable Development Goal 13: climate action
Goal 13: climate action
Sustainable Development Goal 15: life on land
Goal 15: life on land
Sustainable Development Goal 11: sustainable cities and communities
Goal 11: sustainable cities and communities

  1. Installation:

    • Set up the recirculatory system components, including tanks, filters, pumps, and aeration systems, in a suitable location.
    • Ensure all connections are secure and properly sealed to prevent water leakage.
  2. Water Preparation:

    • Fill the tanks with clean water, ensuring it meets the required temperature and oxygen levels for the fish species being cultured.
  3. Initiate the System:

    • Start the recirculation system by activating the pumps. This will begin the flow of water through the filtration process.
  4. Monitor Water Quality:

    • Use water testing kits to regularly assess key parameters such as pH levels, ammonia content, and oxygen saturation.
    • Adjust the system settings or make necessary changes if any parameter falls outside the recommended range.
  5. Maintain Filtration:

    • Routinely clean and maintain the filters to prevent clogging and ensure optimal filtration efficiency.
    • Replace any damaged or worn-out filter components as needed.
  6. Fish Feeding:

    • Provide fish with appropriate feed based on their species and size. Monitor feeding schedules to avoid overfeeding or underfeeding.
  7. Observe Fish Behavior:

    • Regularly observe the fish for any signs of stress, illness, or abnormal behavior. Address any issues promptly.
  8. Record Keeping:

    • Maintain detailed records of water quality parameters, feed consumption, and fish growth. This information will aid in fine-tuning the system for optimal results.
  9. Harvesting and Stocking:

    • When fish reach the desired size for harvest, use appropriate methods to safely and humanely harvest them from the tanks.
    • If restocking is required, ensure that new fish are acclimated to the system gradually to minimize stress.
  10. Routine Maintenance:

    • Conduct regular checks on all system components, including pumps, filters, and aeration devices. Repair or replace any faulty parts promptly.

Last updated on 22 May 2024