I saw this in my main tank this evening. I noticed the tentacles moving and it didn't stand out as a living being since it was white colored. But then I watched it move from the
live rock ACROSS a gap to the astrea snail sitting to the left! I had my camera in hand and got some pictures of it. The last shot is probably the best.
I am thinking it is some type of
Nudibranch or a snail without its shell, but I really don't know. I want to identify it so I can determine if it needs to be removed or not. Thanks!