nudibranch or worm?

[ch33k]

I found it crawling on the glass this morning. I'm not sure how it got into the tank because I dipped all the corals.
Does anyone know if it's bad for the tank?

 

[sixty_reefer]

That’s a slug, definitely put it back they herbivores good cuc

 

[ISpeakForTheSeas]

The little "horns" (rhinophores) on the front indicate it's some species within the Heterobranchia subclass. I have no idea which species (or even general category within that subclass, could be a sea slug, sea hare, or nudibranch), but it's most likely harmless.

 

[ch33k]

Ok thanks for the info