Crayfish should be cared for exactly as you would tropical fish, however, you do not need an aquarium heater. In fact, cooler water is preferable for their survival.
They prefer their tank to have fish in it, so they can apprehend and eat them. This is included on the one hand to make your more successful with the crayfish, but also to warn you that with crayfish in the tank, you shan’t be successful with the fish.
Crayfish prefer to eat fish meat, canned shrimp, frozen blood worms, any kid of convenient and relatively “clean” meat. An example of an inappropriate food source would be fatty roast beef, even though it’s meat. We kept ours alive for their natural adult lifespan with little more than Sanfransico Bay brands’ “Prime Reef” served in chunks.
The ideal crayfish tank would have an inch of gravel on the bottom, some plastic and live plants such as Aponegeton bulbs, a daylength of 16 hours, using full spectrum lighting. The best bulb for full spectrum lighting is the CoraLife Trichromatic bulb. These are available for all the commercially available fluorescent fixtures.
An airstone would ideally be applied to the tank even if it has a good filtration system. The ideal filtration system for a crayfish tank would be a formidably sized sponge filter, perhaps the Tetra brand Bili(tm) or the Brilliant. Lustar V is also a good sponge filter.
Crayfish will hunt and eat by day, and night.
I set up my crayfish with caves to climb into but which permit me to see them sitting inside the cave. Simple slate pieces can be organized into a nice cave.
Crayfish of radically disparate sizes will fight and the smaller crayfish will be the loser. Even in matched sizes, as they mature, you may find a lost claw or other appendage due to skirmishes in the tank. Providing multiple caves and hideouts can be of assistance.
Good luck with the crayfish.