How big is your common? I have one also, about 5 years old. He is super aggressive, has a very deformed shell from previous owner keeping him indoors in a very small enclosure. His carapace is approx. 6" long & flared upwards around the err 1/2 of shell.

He is much happier now in outdoor pond.

I am having trouble finding live crayfish, here in LA area. Lots of Vietnamese crayfish restaurants but none will sell them live. I guess I may have to hit the local rivers & golf course streams.