Nudibranch, good or bad

[Silvergryphon]

<img src="http://i57.tinypic.com/14e13si.jpg">

This a good one or bad one. I'm not 100% sure, I think it may be a zoa eating nudibranch, but I want verification before I go tearing everything apart to eradicate them.

 

[pagojoe]

Bad.

 

[Sugar Magnolia]

Yep. Aeolid nudibranch. http://www.reefkeeping.com/issues/2005-05/rs/index.php