I only ask cuz I think my ruby crab ate my coris wrasse while it was asleep. When I first got the wrasse he would bury himself at night, then I guess he got comfortable cuz then he just started to lay on the sand to sleep at the back of the tank with his back facing out. Didn't think much about it at first, but after a about a week of that, I found him dead with a chunk missing out of his back!! I think the crab came across him while he was sleeping on the sand.
Obviously, no more wrasses for me in that tank!!