My crayfish is a big baby. Hes, 6-7" in a 30 with several 1-3" tetras, rams, cichlids, plecos, cory, and all he does is just sit around, haha. He wont even eat frozen silver sides when I would offer him them. I honestly did not know what he was eating for a few weeks. I now have him eating Massivore pellets, which is good but expensive, but I love the little guy, so what can you do.