Crayfish are no different from other aggressive fish?
They are territorial and aggressive during feeding, simple steps like a large enough tank with sufficient hiding places, he will be rather peacefull and won't bother other bottom dwellers unless they come into his space.
I have my established 29 gallon tank and I have a 6 week old 20 gallon now, with Turqouise Gourami's & a Pleco, waiting to be transfered into my 55 gallon once it's fishless cycle completes.
I have a blue crayfish and he is never aggressive towards the fish unless they try swimming into his wrecked ship or unless they try snatching food that is in front of him. I usually toss him a pellet of shrimp and make sure he gets it before it breaks apart. Haven't had a single pinching incident yet.
They are nocturnal and will be really active at night, my crayfish will roam the bottom of the tank all night and he does not bother the pleco at all. If I go sticking the vacuum in, he comes out and attacks it, it's pretty funny
