I have noticed that some of my sea mats polyps contract for now apparent reason since yesterday. On closer inspection the closed heads each had a small yellow/green nudibrank (it has frills so I assume it is) on it. It looks like the nudi’s are eating the small tentacles of the polyps and leaves behind a “acid burn” mark. The individual polyp seams to be ok in a hour or two after the nuni has left. 1. Do I have to remove them or will the coral manage? 2. How do I remove them?