I have 2 that I got from Etropicals..about $7 each as part of the build your own package. They are gorgeous and active, but they don't touch hair algae. They just skim over the algae on the glass. I just got a sea hare in the hopes it eats hair algae, but so far, no....just skims over the glass. Take care, Eric
Last year I raised over 100 of them. They are lettuce slugs (elysia crispata) there are no lettuce nudi's. They eat bryopsis and very little hair algae. Even with over 100 of them in my reef I still had HA.
Here is an article I wrote about them. http://www.breedersregistry.org/Articles/baldassano2004/SolarPoweredSlug.htm