Starfish - acro eater? Please ID

[choss]

I noticed recently that two frags of the exact same acropora were healthy one day, then completely white a few days later. I checked parameters and everything was stable. Al the other frags are fine. Then two days later another millepora in the same section of the frag tank experienced the same issue. I removed the frag and there was an asterina starfish under it. A quick search on the other white acro frags I found another. I checked all my frags and removed around 8-10 more. I know people have different views on whether they are friend or foe. These are not as white as the ones I usually get in my display tank. They are a bit more brown with flecks or red. Here are a few pics. Would love an id if anyone out there has experience with these.

IMG_7500 by Chris Hoerenz, on Flickr

IMG_7501 by Chris Hoerenz, on Flickr

IMG_7502 by Chris Hoerenz, on Flickr

 

[Flippers4pups]

Could be the culprit. Remove them when seen.

 

[Orko]

I have heard the same thing they "could be acro eaters" other people say they are fine .. when I see them in my tank I remove them just to be safe.

 

[choss]

I picked up a harlequin shrimp. Gave him one of these while acclimating him and he immediately made short work of it.