Well crayfish don't actually eat waste so you shouldn't choose based on that alone. In the end, no fish is safe to keep with a crayfish unless you have a larger tank as he can and will eat them. So on that basis I say pick up some guppies as a tank mate. Guppies breed fast and easy so if he eats some they get replaced on a regular basis.
For lighting I believe that they dislike light, though I could be wrong. Just make sure he has plenty of places to hide and he'll be fine either way.
Also be careful with the lid to the tank. Crayfish are notorious for escaping tanks with gaps or loose lids!
For lighting I believe that they dislike light, though I could be wrong. Just make sure he has plenty of places to hide and he'll be fine either way.
Also be careful with the lid to the tank. Crayfish are notorious for escaping tanks with gaps or loose lids!