Yeah SWfish lists them under nudibranchs but they really are in the sea slug family (not much of a difference). The main reason they don't live long is because they always seem to find a way into powerheads. I have heard somewhere that if they eat enough algae, they will start using photosynthesis and gain around half of their nutrients from that. Also I think they're favorite food is bryopsis (sp). If you tried covering your powerheads with sponges or something give them a go, it's not like they're very expensive or anything.