What kind of nudibranch?

[havtern]

Hey
I just got some live Rocks and found some kind of nudibranch on them. Hope someone can tell me if they are bad or not and what kind of coral they will if they are bad.
Hope the picture is okay for id.

 

[Benjammin]

Found this:

Photo Ark: Opalescent Sea Slug

Fierce and colorful, the opalescent sea slug (Hermissenda crassicornis) is a nudibranch to look for in the tide pools along the Pacific coast.

www.nationalgeographic.org

 

[NashobaTek]

@vetteguy53081 might know

 

[monkeyCmonkeyDo]

Berghia or montipora eating. 1 or the other. Lol.
D

 

[ATAquariums]

Where did you find them

 

[Hairyteeth]

Leaning towards montipora eating nudibranch

 

[vetteguy53081]

Being a monti eating nudibranch, they are one of the hardest to spot on the skeletons of the coral and are destructive, As in the pic below, you really have to look well to spot them. You can if very few, siphon them with a 1/4" hose and discard them. Then comes the eggs which are even tinier but usually in clusters. You have to scrape them off outside the tank. There is nothing that will kill them.
Good news is dips will work on killing the nudibranchs. Bad news is that will go after some Acro once they strip the monti coral.