It has long been assumed by most that Asterina starfish only ate the dying segments of corals such as Monti digi and acropora or the algae that were invading a dying coral. I have evidence that this is not correct;
http://i1269.photobucket.com/albums/...1/60d4b1c5.jpg
This next pic clearly shows the band of eaten polyps after I removed the star with a large wooden skewer. This was a healthy area yesterday.
http://i1269.photobucket.com/albums/...1/7d13572f.jpg