Mine is the same way. I have a sand bottom and he digs a nice little cave in it where he hangs out all day-- until food arrives. I did notices that when he had a mate they ventured out more, but she decided to jump out of the tank one night to explore so now he's alone again..Nothing to worry about unless they won't come out for food. Mine hang in the back right corner together but if I were to drop food on the other side of the tank, they dart over to it and quickly back 'home' to their side lol