Yes, he will eat them eventually. I had one that ate platies, so they can eat even bigger fish. Plus they hide constantly, so you will never see him except occasionally at feeding time. but I guess the cool thing is every time you see him you'll notice he grew. I ended up putting mine in an unheated tank with severum (? if I recall correctly, or maybe NA sunfish) and pardise fish, and he did great in there. It was always a surprise when I'd see him every couple weeks because I would forget we was in there!