I have a 9" grass pickerel and he is pellet trained, he stays in a 75g during the winter and in my 400g goldfish pond during the summer, he doesnt bother the goldfish but does feed on the shiners that breed in there. I doubt that he would eat a creek chub as they are fairly fast and active, the only thing that i would be concerned about would be that the chubs would stress the pickerel due to so much movement. What size tank are looking at putting him in?