Crabs

yeah, we call them spotted cats.

Our Channel & flatheads (locally) are a greenish/silvery color. Our channel cats are also blueish grey they favor blue cats but are channels.

channel.jpg
 
My lfs sells what they call gold fiddler crabs, they stay relativley small, will eat almost any fish food, are excellent scavengers. the can stay in water fully submersed or live outside to the best of my knowledge. Do some research on then, i dont know a super lot about them.
 
lol...those blue crabs that reddog posted are being sold at this vietnamese grocery store near me in chicago....live ones!
 
AquariaCentral.com