ID Nudibranch, good bad??

[aquajeep]

thats prob what happened to the yellow colt coral we had and maybe a good portion of xenia thats gone missing. i rem seeing this guy in the tank this time last year but it was so small i thought it was a sponge lol now its pretty good size.im going to put it in a container and see if it eats anthilia.i have too much of that stuff lol