I doubt he will actually try to leave the tank, but I have never known them to climb glass. Mine always stays on the bottom in the live rock. I wouldn't chance it though, I would try luring him down with some food.
Mine started climbing the glass, out of the blue, after having him for about a month. It turned out that I was having an ammonia spike and, I guess, it wasn't as bad up high in my tank.
He must have gone back to the bottom of the tank b/c I didn't see him on the floor this AM. He might be behind the tank, but I doubt it. He has done this before but never for as long as he had last night.
Thanks for the conversation.
