ID Please...Hitchhiker?

[mosssw]

It is about 1/3" long. Is it good or bad? Thank you,

 

[pagojoe]

Bad.

 

[chrisstie]

It's definitely a nudibranch. I'm not sure of the species but I'm sure someone will chime in.

Where did you find it in your tank? It looks similar to the bad ones you can find munching on zoas but.. to me it also looks like the good kind that eat aiptasia but I have a very untrained eye.

 

[Don-Coraleone]

pull it out. dont take any chances.