Hitchhiking sea slug

[Seahorse man]

Hello everyone! Hope you are all staying safe and healthy!
I recently added a few corals to my 5 gal frag tank and today I spotted this little guy. He is very brightly colored and I did manage to catch him and pull him out of the tank, but I'm hoping he is a good one, but I doubt it. I know that there is a very slim chance of getting a positive ID on it, but I'm still curious. Will he eat corals? Could this be why one of my zoa frags refuses to open? Thanks for the help in advance!

 

[Crabs McJones]

Nudibranch, if your zoas are affected then i'd guess it's a zoa eating nudi

 

[Seahorse man]

Nudibranch, if your zoas are affected then i'd guess it's a zoa eating nudi

I've got three frags of the same zoas, and 2 opened beautifully, but one doesn't want to open. I'll try a dip on the zoas and see what happens.