Hitchhiker ID please Good or Bad

[StarBuck]

Received coral shipment from LFS yesterday and this thing was attached to bottom a frag disk. I have it isolated, I have never seen anything like it....is it good or bad? it's 3/4" long. slug, cucumber, nudibranch.

 

[tmcca]

Looks like a cucumber. Does it have tentacles on top of it's head? Looking at it closely looks like a Navanax Sea Slug.

 

[tmcca]

I think it's a sea slug and bad! Not reef safe because they will devour your clean up crew.

 

[ISpeakForTheSeas]

Received coral shipment from LFS yesterday and this thing was attached to bottom a frag disk. I have it isolated, I have never seen anything like it....is it good or bad? it's 3/4" long. slug, cucumber, nudibranch.

Welcome to Reef2Reef!

That is an Arminid nudibranch (taxonomic family Arminidae), probably a Dermatobranchus species - these eat some corals:

The creature above looks like Dermatobranchus striatus, but with a white head and slightly more white-spotting. It might be a different species (there quite a few in the genus, including some that don't have official names yet), but I'd be surprised if it's not a Dermatobranchus sp.
https://en.seaslug.world/species/dermatobranchus_striatus

they're octocoral-eaters, so they may feed on softies, GSP, gorgonians, etc.

 

[DSC reef]

Agree with above, bad nudibranch

 

[StarBuck]

Thanks Guys looks like you ID , the little bugger... not going to take a chance with it snice I am Softy heavy......