Growth of small scale aquaculture in East Africa has been limited by cost of feeds and management strategies related to lack of appropriate technologies. The objective of this on-farm trial was to propose the most profitable and practical pond management options and to test them on farms to evaluate their profitability and repeatability. The trials began in December 2020, and were conducted at four farms in Central and Eastern province. All ponds, including lined ponds were treated with agricultural lime prior to stocking. Ponds were then stocked with sex reversed male Nile tilapia, Oreochromis niloticus (2.5- 4.5 g) at 3 fish/m-2 followed by an addition of clarias at 0.3 m-2 three months later. All treatments used fertilizer (DAP and urea) to produce natural food for the tilapia and the fish were offered different qualities of supplemental feed to complement the natural food derived from the fertilizer. Three supplemental feeding protocols were tested: TRT1, wheat bran (about 16%CP, cost $0.25 kg-1); TRT 2, low protein feed (25%CP, cost $0.85 kg)-1 ; and TRT 3, high protein feed (30-32%CP, costing over $1 kg-1) fed at half rate. Weekly water quality monitoring included temperature, dissolved oxygen, secchi disk visibility, pH and occasionally, total alkalinity and total hardness. Fish were fed twice daily, according to a feed table and fertilizers applied weekly, until May, then suspended. No aeration was used and ponds were static except for topping off from evaporation or seepage.
The higher protein feed given at half ration resulted in the most reliable net revenues per are (100 m2). However, because management was highly variable, some farmers found the bran plus fertilizer treatment to be highly profitable. Farm management differences included low survival due to bird depredation (farm 4); overfeeding beyond the set protocol (farm 1, HiPro), and low fish recovery due to incomplete pond draining (farm3, all treatments). Previous surveys that showed very low to negative profits from pond fish farming were likely based on farmers who purchased the less expensive floating feeds and fed at high rates, with no fertilization. Farmers need to be taught to only use feed tables as a guide and to be conservative on feed use. The individualized farm advising provided during the trials helped participating farm managers increase their understanding of pond management, feeding and water quality management.