The trend of fishermen fishing in major water bodies and small streams has since changed, with many adopting aquaculture. Although highly appreciated, experts think farmers must further adopt aquaponic farming to harvest both fish and crops – mainly vegetables – of their choice. Aquaponics is a sustainable food production system as it combines aquaculture – rearing fish and hydroponics, which is growing plants in a soilless setting.
It creates a symbiotic ecosystem where nutrient-rich water from fish tanks is used to fertilise plants and the plants in turn, filter the water to be recycled back to the fish tank for their growth. This integrated approach reduces water usage and eliminates the need for chemical fertilisers, making it an environmentally friendly and efficient method of food production. This is what scientists at the National Fisheries Resource Research Institute (NaFIRRI) Aquaculture Research and Development Centre, Kajjansi are advocating fish farmers especially in urban setting to adopt.
Aquaponics research initiative
Dr Barry Kamira a research officer at the Institute explained that the aquaponics research project at the Institute is a two year project being conducted under a major project called Pr AEctiCE funded by the European Union. This study arose out of the need to sensitise urban fish farmers about the importance and advantages of adopting aquaponics fish farming which leads to farmers harvesting fish and crops as well. The project started in 2021 and it will soon come to an end with promising results. The scientists will disseminate the information by bringing farmers on site to learn how to set up aquaponics farm.
How the structure is set
Mr John Bolingo, a technician handling the facility at the Institute explained that tanks are filled with water where fish fingerlings are left to breed.Meanwhile there are structures in form of beds filled with stone gravels through which water from fish tanks runs through and in the process is filtered. However, the water from the tanks runs to the plant beds filled with nutrients from the fish tank and by the time it is filtered to run through a pipe back to the fish drums, it is clean water. The steps are that Fish produce waste in the form of ammonia through respiration and solid waste. Beneficial bacteria, living mostly in the biofilter and on media surfaces, convert ammonia into nitrites and then into nitrates, a form of nitrogen that plants can easily absorb. The plants take up the nitrates as nutrients, which supports strong, healthy growth.
As the plants absorb these nutrients, the water is naturally filtered and cleaned. This clean, oxygenated water is then recirculated back to the fish tank, creating a continuous cycle. The result is Healthy fish growth and thriving plants including a self-sustaining ecosystem that requires minimal external inputs. The adopted fish for the trials is Nile Tilapia and cat fish while the crops are spinach, tomatoes and Lettuce.
The cycle
Fish are raised in a tank and their waste, primarily ammonia is converted into nitrates by beneficial bacteria. These nitrates are then absorbed by plants in a hydroponic system as a natural fertiliser. The filtered water is then recirculated back to the fish tank, completing the cycle. The scientists have done the trials and realised that cat fish grow faster and better in this setting compared to Nile Tilapia. However the facility will continue to perform because it is meant to sensitize farmers interested in adopting aquaponics farming. Farmers are advised to seek advice from them before setting up aquaponics farm.
Types of aquaponics set ups
Nutrient Film Technique (NFT): Efficient but better for advanced growers. It uses narrow channels PVC pipes or troughs where a thin film of nutrient-rich water flows over the roots of the plants. It’s a space-saving method, often used in vertical or indoor systems. Raft System or Deep Water Culture (DWC) Best for leafy greens and commercial growing. The systems float plants on a sheet of foam over deep troughs filled with nutrient-rich water. The roots dangle directly into the water, absorbing nutrients continuously In this system the fish waste us filtered before reaching the grow bed because air stones are used to oxygenate the water to prevent root rot Hybrid and Vertical Aquaponics Systems: Many aquaponic gardeners experiment with hybrid systems that combine multiple methods, for example, media beds for fruiting crops and raft beds for greens.
The benefits of aquaponics
Aquaponics is not only a highly efficient way to grow food, but it also comes with a range of environmental and practical benefits that make it an attractive option for eco-conscious gardeners, urban farmers and those interested in sustainable food production. It saves up to 90 percent More Water than Traditional Gardening and it is chemical free because no synthetic fertilizers are used.
It is Eco-Friendly Farming Solution
Aquaponics is widely regarded as an eco-friendly farming method because of its efficiency, sustainability and lower environmental impact compared to traditional agriculture. Waste reduction: Fish waste is turned into plant food, and plant waste can be used as feed for fish in some systems, closing the loop entirely. No soil degradation: Aquaponics avoids the issues of soil depletion, erosion, and the need for large swathes of land that conventional farming requires. Lower carbon footprint: With reduced transportation needs (especially for urban setups), aquaponics can contribute to more localized food production, reducing the need for long-distance food transport.
Food security
By using aquaponics systems, you can grow local, fresh food in urban areas or even on rooftops. This contributes to food security by providing people with access to healthy, self-grown produce right where they live.
Common challenges and solutions
While aquaponics offers numerous benefits, it’s not without its challenges. As a closed-loop system, aquaponics requires careful monitoring and maintenance to ensure the fish and plants are thriving together. Farmers must continue to monitor the water Ph yet fish and plants have different pH requirements and imbalances can lead to poor plant growth, stressed fish, or system inefficiencies. The solution is for farmers to conduct regular testing by using a good-quality pH metre or test kit to regularly check the pH levels. If the pH is too low farmers can use baking soda to raise it
Fish Health is directly linked to the health of the aquaponic system. Sick or stressed fish can disrupt the balance and reduce system productivity.