I think they are very neat. Short lived, specific eater once food gone they are gone. They like to get into powerheads and get shreaded. Other than that really cool looking slug.
Thomas
the lettuce ones are algae eaters, other colored ones eat a varied diet of sponges, algaes,and corals,I have had these guys 3+months so far and they have eaten some sponges in my tank
Nothing I have seems to bother them, I saw at a LFS a brittlestar try to eat one and spit it out, the only complaint I have is they can fit into very small places and get in my sump time to time