in my own opinon i would move the crayfish to his own 5 gal
tank. I had a cray for about 5 days and he was not shy about going after my bichir and trying to nip at him. I suppose my bichir got his revenge; the day i had the 5 gal
ready to move the cray fish in my bichir got to him first...o well. Back to the point, BGK are very passive fish. I would make sure that your cray doesnt end up nipping him. My bichir took a chunk out of my BGK's tail. It healed, but obviously they arent very quick to respond to an attack. Plus, they are blind so its hard for them to see whos coming or where they are going. They just feel there way around.
What size tank are you keeping yours in?