Due to the recent problems of higher fuel costs and exhaustion of marine resources, fish meal-free feeds have been developed. However, these feeds are insufficient from the standpoints of feed-intake and growth of fishes. Also, there has been required a feed which can economically and easily prevent or treat fish diseases and, even in the case of given in a reduced amount, ensures efficacious fish growth without disturbing the growth of fishes. Disclosed is a feed containing fly pupae and/or fly larvae. This feed can be taken at a high feeding rate by fishes, promotes the growth of the fishes having taken the same and exerts an effect of activating the immunity of the fishes.
