Originally Posted by Sensfan
Everyone tends to think crustacean a are unfriendly to fish.. I have a blue crayfish in with ghost shrimp and rasbora's and he's hasn't been an issue at all. Occasionally herds away the shrimp but pays no mind at all to the fish.
A full sized crayfish can, and will eat, kill, maim, if it feels like it and it is a fact, you shouldn't have any expensive, prized, or very much loved 1-2", maybe even 3" fish. He could get bored or hungry, you just can't be safe with them. Though I gave may friend a Blue cray for her birthday and he had his corner and didn't ever seem to bother anyone for the years of his life.
Just don't want anyone to bring one home and end up with a massacre! They can have different personalities like people do, and snap, like people do.