They are more like Nudie Brancs than conches, i can see how the back of them does look like a shell but its actually just their slimy little back. Seen loads diving stuck to Goinoporas, but if you have a system that can grow Goinoporas at a rate that could support these little guys munching on them then you officially deserve the title of Grandmaster Reef Keeper. Glad to see your concern has lead you to check here first, those LFS can be such a tease. "Buy me, buy me"... they whisper........Best let some ignoramus kill it, such a shame. Mind you chances are he was probably a hitch hiker, still shame.