Is this a sea slug?

[Cchamberland]

Found this on the glass this morning, and put it into a sample jar for now. What is this and is it coral safe? If so back in he goes!

 

[CocoReef]

Looks like it might be a lettuce nudi but not positive on that ID. I'd keep it if you arent seeing any problems

 

[formallydehyde]

It's almost definitely a sacoglossan sea slug which makes it an herbivore. I *think* it's an Elysia species. It looks very familiar to me, I think from an Elysia species I've seen in pictures, but not one of the more common ones vendors sell, but I am blanking on the name. If you don't have whatever specific types of algae it eats (bryopsis seems to be the most consistent for the genus, but there's a bunch of species that specialize in other stuff) it's unfortunately going to starve. That wouldn't have any negative consequence for the tank though.

 

[Cchamberland]

It's almost definitely a sacoglossan sea slug which makes it an herbivore. I *think* it's an Elysia species. It looks very familiar to me, I think from an Elysia species I've seen in pictures, but not one of the more common ones vendors sell, but I am blanking on the name. If you don't have whatever specific types of algae it eats (bryopsis seems to be the most consistent for the genus, but there's a bunch of species that specialize in other stuff) it's unfortunately going to starve. That wouldn't have any negative consequence for the tank though.

Copy that, thank you! It was a hitchhiker to begin with, but it still sucks to know it's going to stave.

 

[formallydehyde]

Copy that, thank you! It was a hitchhiker to begin with, but it still sucks to know it's going to stave.

Assuming it came in on live rock, there's is a slight possibility its food source came with it, but what that is I don't know. It would be some type of macro algae or semi-complex algae. But yeah, it sucks but it happens.

 

[ISpeakForTheSeas]

Yeah, Elysia sp. Sacoglossan Slug - sometimes called Lettuce Nudibranchs (though they're not actually nudibranchs at all):

Elysia flava or E. obtusa - harmless/beneficial Sacoglossan slugs. They're herbivores, with E. obtusa known to feed on Bryopsis, while E. Flava is thought to feed on Cladophora. As mentioned below, I don't know if these are required feeds or just strongly preferred feeds:

Some lettuce slugs (typically from the genus Elysia) will eat nuisance algae species, but their wild diet varies pretty drastically from one species to another, and some species have some pretty specific wild diets (I don’t know if these are required diets or preferred diets, but Reef Cleaners reports that they'll eat just about any green, fleshy algae). That said, Elysia slugs generally feed on siphonalean algae such as Caulerpa, Codium, Acetabularia, Halimeda, Udotea, Byropsis, and Valonia spp. So, in theory, these guys should eat nuisance algae that pops up in your tank.