Snail ID help

[TommyK]

Good or bad?

 

[Reefkeepers Archive]

That is not a snail, that is a nudibranch, it isn't a zoa eating or monti eating one, but I'm unsure whether it's harmful or not, @ISpeakForTheSeas?

 

[Sophie"s mom]

Agree with reefkeepers! Nudibranch for sure

 

[ISpeakForTheSeas]

Not technically a nudibranch in this case, though they're sometimes called Lettuce Nudibranchs because they look so similar - this is an Elysia sp. Sacoglossan Slug; an algae eater:

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.