I bought a HOB refugium off a guy on craigslist. He asked me if I wanted a sea urchin too, of coarse I took it. Well once I put him in the tank he was moving fine, then yesterday he moved to the sand bed in the back of the tank and stopped moving. I attempted to move him with a net and some of his needles were still moving. It doesn't seem as if any have fallen off, but he hasn't moved. Is he on his way out, or could it be he has to acclimate to my water?