Fish take semi-circle *****s out of the clam mantel. Get that fish out or kiss your clam goodbye. I got a yellow Coris wrasse way early in my reefing career that just go crazy after 6 months and took chunks out of my clams. Fortunately, catching a Coris wrasse is easy in a sand bed tank. See where he dive into the sand and just dug him out there once you scare him into diving into the sand.