<![CDATA[Ketapang seeds are a plant-based ingredient that has the potential to replace soybean meal in fish feed due to their high protein content. This research aims to determine the effect of using ketapang seed meal fermented with Rhizopus sp. as a substitute for soybean meal in feed to improve the efficiency and growth of tilapia. The method employed was an experimental design with a completely randomized design (CRD), consisting of one factor with 5 treatment levels and 3 replicates. Five types of feed were formulated to contain 35% protein, with feed P0 containing 100% soybean meal (control), and feeds P1, P2, P3, and P4 replacing soybean meal with fermented ketapang seed meal (TBKF) at levels of 25%, 50%, 75%, and 100%, respectively. The fish used were tilapia measuring 4-5 cm and weighing 2.01±0.29 g, which were placed in fixed net cages measuring 1 × 1 × 1 m with a density of 25 fish per cage to measure fish growth and 10 aquarium units with a stocking density of 20 fish/aquarium to measure feed and protein digestibility. The test feed was administered at a frequency of 5% of the test fish biomass, three times a day at 08.00, 12.00, and 16.00 WIB, for 56 days. The results showed that the use of fermented ketapang seed flour in feed had a significant effect on feed efficiency, protein retention, and specific growth rate of tilapia fry. Based on the results of the research, the use of 75% fermented ketapang seed flour in feed produced the best values for feed digestibility (56.90%), protein digestibility (69.99%), protein retention (36.96%), feed efficiency (61.36%), specific growth rate (2.49%), and fish survival rate of 98.67%.]]>
