Hmmm... mbuna (like yellow labs) hide in rock caves on the bottom of the tank. Crayfish injure and kill fish who stray into their reach... on the bottom of the tank.
I would not put crayfish with my cichlids... even if I lived in Texas. (I don't understand how one's geography would stop fish from behaving normally... like crayfish catching whatever they can...) Bad idea, IMO.
Jim