I have them too. I asked the LFS
what they were (they had them too) and they told me that they were tiny feather dusters that don't grow beyond the size of a pencil eraser. If anyone disagrees please correct me, just going off the info that I got.
Marlin: Okay, a mollusk walks up to this sea cucumber, well he doesn't actually walk, he's just there, and he turns to the sea cucumber, and... Well, wait, there's a mollusk and a sea cucumber and...
Chum: You know for a clown fish, he's not that funny.