With increased investments in aquaculture, challenges of inadequate fish feeds have necessitated the identification of suitable alternatives for fish meal , wheat and corn in fish diets to take care of the protein needs of farmed fish. Seaweeds are receiving attention as suitable alternative protein sources for farmed fish . In a 12-week feeding trial, t he effect of 2 seaweed supplimented meals ( C. crassa and U. rigida) on growth performance and body composition of Nile tilapia fingerlings was investigated. This was the first attempt to utilize seaweeds C. crassa and U. rigida as feed supplements for Nile tilapia in Kenya . The experiment was done in hapas placed in earthen ponds in four replicates for each treatment. The fish were fed to apparent satiation with fish meal supplemented with various levels of C. crassa and U. rigida meals (5%, 8%, 10%, 20% and 30%). A diet without seaweed served as a control. Determination of carcass nutritional composition was done at the beginning and end of experiment. Fish weight and length was taken for each treatment every two weeks.
The highest weight gain was observed in fish fed the 8 % U. rigida and C. crassa supplemented diets while, the lowest weight gain was recorded in the 30% C. crassa supplemented diet. There were significant differences (p<0.05) in specific growth rate, feed conversion ratio and protein efficiency among the treatments. Protein utilization tended to decr ease in the groups fed the seaweed meals at the highest supplementation level of 30 %. Carcass lipid levels increased with increasing levels of U. rigida and C. crassa meal s. The results suggested that both seaweeds U. rigida and C. crassa meals could be used in small percentages in tilapia diets.