I've had quite a few of these in my tank & not sure where they came from. As far as I know they came in with some of my original lr. Today I noticed that one was on a leg of my sand sifting star. While doing a water change I decide to just scoot him off of the bigger starfish and dicovered that it was actually eating it! There is now a good size chunk missing out of the leg of the sandsifter. As long as they have both been in the tank, I've never noticed this & actually don't think that it has happened before, has anyone else experinced this? Also, what can I do for the sandsifter now? Any help would be appriciated!