I believe that I have the type of asterinas that are eating my zoanthids, they're a little hard to see but they are in this picture. I've seen a few of the white ones in my tank for a long time now but these are darker in color. Aside from getting a harlequin shrimp what else can I do to get rid of these? The zoanthids in the picture were previously completly covering the rock but they have started dying and leaving bare spots


