Please identify

[furrymurray]

I noticed this little guy a couple of weeks ago and he is growing pretty quickly. Is he a good guy or a bad guy? I usually just see him on the glass. Thanks for your help

 

[mr_X]

It's a nudibranch. Not sure if it's good or bad. Do you have any zoanthids in the tank? If so, check the colony for more of them.

 

[furrymurray]

I do have zoas. I will check for more then. Thanks Mr X