i currently have a 15 gallon tank with 5 bronze cories and an african butterfly fish. the local fish store has a tank of crayfish with that label only so i am not sure what type they are. they dont have much color at all. the question is would i be able to keep a crayfish in the tank with my cories. i am not worried about him catching the butterfly fish because he stays at the top constantly. would this set up work??? or i could get a crab which can live a good while in freshwater but needs land (which is a hassle)