if he will eat the krill and bloodworms at that size only feed him that. and then down the road maybe try to get him on something like azoo 9/1, i like that food. alot of times fish at that size can be picky thogh and only want live little fishies to hunt down and eat. you want to form an eating habit of anything but live eventually, so the earlier you can get them off live fish the better off the fish are. however, like it has been said alot before, just fatten them up on whatever they will eat right now because he is small at 3" and just needs to eat eat eat weather it be live fish, krill, pellets, or whatever, just keep him full! haha!