I noticed my two cleaner shrimp have made a habit of lounging on my rock is zoanthids. Not picking at anything ... just hanging out on top of them. They seem to be on the zoanthids all the time -I am growing concerned as the zoanthids close, and remain closed as long as the shrimp are there. Has anyone had this happen to them? I'd hate to evict the shrimp, but I will if need be.