I'm not a salt-water person, so I'm not familiar with them (I wondered if this post wasn't similar to some of DMD's before I read it
). However, after looking them up they look really cool and thier variations are very eye-catching!
This bit from Wikipedia was really interesting "The surface dwelling nudibranch, Glaucus atlanticus is a specialist predator of siphonophores, such as the Portuguese Man O' War. This predatory mollusk sucks air into its stomach to keep it afloat and using its muscular foot it clings to the surface film. If it finds a small victim Glaucus simply envelops it with its capacious mouth, but if the prey is a larger siphonophore the mollusk nibbles off its fishing tentacles, the ones carrying the most potent nematocysts. Like some others of its kind Glaucus does not digest the nematocysts; instead, it uses them to defend itself by passing them from its gut to the surface of its skin"
Is this something you're thinking of for your tanks?