My Tree coral. I went to remove it, and there was actually Two, one large one and one small one.
These look similar to the Berghia Nudibranch, But they are not the same. These have feather like apendages where the Berghia's have bulbous like apendages.
I did take a few pictures, but my camera is not so great and due to the light from the tank, and the flash and everything, the pictures are not so great.
But they may give you some idea of what they look like.
I did Bag them up, and plan to Keep? them some how.
I have an 8 gallon with a small cardinal, i may throw them in there for further investigation.
Never have i heard of a soft coral eating nudibranch, and I have been reefing' for 10 years now.
The slugs were found on newly bought coral.
My LFS is reliable, but I guess they put in a couple of infected pieces.