My plain old green run of the mill urchin really cleans the coralline algae off the rocks as well as anything else he finds tasty. I sort of have a soft spot for it as he was one of my first purchases when I set up my 46 gal over a year ago. He also carries stuff around with him, including a part off my power head when it fell to the bottom. I don't know whether to keep him in the tank at the sake of the algae or move him to another tank,or the fish store. Any suggestions...?