DEVELOPMENT OF LOW COST AQUAPONIC SYSTEM IN KENYA

The University of Eldoret activities involved the design and testing of a low-cost aquaponic system that can be used for training, extension and by small-scale fish hobbyists in water deficient situations and urban/semi urban areas where land is scarce. An aquaponics prototype was developed and its efficiency assessed using different fish stocking densities. The system consists of a rectangular fish culture tank raising to 460 mm from the bottom and a plant bed raising to 270 mm from a raised platform, both units being arranged in a vertical tier. Water overflow from the fish unit is passed through a bio-filter made of cut plastic material to increase the surface area. This unit acts as a nitrification chamber before the water is pumped back to the plant unit using a submersible lift pump as shown in the appendices. Water discharge from the plant unit flows back to the fish unit by gravity thereby elimination the need for double pumping. The prototype unit was tested using all male tilapia (Oreochromis niloticus) fry for 35 days to the fingerling stage. Results from the trial show that fish stocking density has an effect on the nutrient budget of  the system. High nitrate content in the fish unit was associated with high stocking density of 80 Fish/T as compared to 60 Fish/T. The nitrification unit exhibited high efficiency since ammonia was not detected in the plant bed. Quantities of ammonia detected in the fish tanks after 35 days was close to the target values of zero. All important water quality parameters for aquaponics system such as DO, pH, alkalinity and Temperature were within optimum values, it is concluded that the system is viable and self regulating in terms of nitrogen cycle. The only limiting factor is the provision of other nutrients required for plant growth by supplemental fertilization. This report provides both design specifications and technical drawings of the aquaponics system developed during this activity. The unit offers good opportunities for rapid commercialization by the private entrepreneurs but there is need to improve on energy requirement through solar technology.