Please ID....nudibranch?

[TNsaltwater]

Just got an eight pound live rock yesterday and found this fellow in the tank today. I was thinking some sort of nudibranch. Please ID (good or bad?).

 

[LeslieH]

Nudibranch & bad. Very similar to the zoa-eating branch that can decimate colonies.

 

[GerritM]

Probably an Phyllodesmium sp. (not so good for an mixed reef tank)

 

[marinoob]

here is some video i have from my usb microscope, same thing....

the color in the sacks is whatever they have ewaten lately. he had radioactive dragoneyes for dinner. i was told zoas eating nudibranches. i get rid of them for like 6 weeks at a time. every 6 weeks i have to dip like 3-4 rocks.

http://www.youtube.com/user/wildpony93?feature=mhum#p/a/u/2/qlBnpEMzNX0

http://www.youtube.com/user/wildpony93?feature=mhum#p/a/u/1/VRenf8OWE2M