In the present study, feed efficiency was affected by water temperature, fish meal level, and their interaction (Table 2). At 178C, feed efficiency was significantly higher in fish fed the fish meal diets than fish fed the all-plant-protein diet. However, the improved feed efficiency in fish fed fish meal diets at 178C did not result in significant increase in weight gain. The reason
for this is not clear. Although there were significant differences in the weight gain of fish fed various levels of fish meal at 218C and 278C, no significant differences in feed efficiency were noted. This could be caused by the variation in amounts of feed offered in excess among tanks. Fish were fed to apparent satiationby visual examination, but the slight excess of feed remained, if any, was not removed from the tank.