Need ID on Worm - May be Culprit for Damage to YCG's Fin

[leluckie]

Hey all - I've been scouring the internet to try to find an ID on this worm and an answer as to what could be wrong with my YCG's tail fin.

 

As of yesterday, the YCG's fin was perfectly fine, but when I came in this am there seemed to be some damage. The Zoa polyps I have in the tank have also been closed for most of the day and have been open and happy since I added them to the tank last week.

 

I spotted this worm (?!?) prior to the lights coming on and need an ID so I can properly treat the fish/take steps to remove it from the tank.

[WhatsReef]

Those fins are pretty hacked up... I doubt a worm could have done it because one would think that once it bit his tail he'd presumably be able to quickly escape and shake the worm off if it was attached... he probably wouldn't just let the work snack on his tail, naw mean?

 

Are there other fish in the tank that might be nipping at your goby?

[WhatsReef]

It seems long and thing to be a nudibranch, but some are longer and thinner. Where you able to notice antennae on it?