my diamond watchman sifts ALL day long. doesn't really throw sand on my corals however he and I did have a mexican standoff for a few days. i had a lobo that was mounted on a piece of ceramic tile and the little bastard kept digging underneath it. the only problem was, he'd then pile up all the sand on top of the lobo literally covering the thing up. I'd clean it off, move the lobo and then wait. soon as i'd leave the room, he'd sneak over and start doing it again so before he'd get too far along, i'd clean it off, fill in the cave underneath and start all over again and again. finally had to remove the tile and put a little bit of JB water weld putty around the base to help the lobo stand on its own and the diamond finally leaves it along. The whole thing was more comedic than anything else. fortunately the lobo is fine and he hasn't messed with any other corals in my sand.