Crayfish care, mates and housing?

crayfish are highly aggressive, speaking from personal experience I had a crayfish live with 2 6 inch piranhas for over 3 months before being eaten, they eat what they can catch Ive seen them eat goldfish before so anything slow will be killed so Id p on the snails and the fiddler crab and crayfish will more then likely fight with the last one with claws being the last one to live. sand also looks nice with crayfish IMO for tankmates a 10 gallon might be too small id go for fish it either cant fit in its claws or fish it will never be able to catch with may be hard considering they have to sleep or will die from stress from running/swimming away constantly