Hitchhikers

[digital-audiophile]

Sounds little little brittle stars, just about every aquacultured piece seems to have them.

[Myka]

Yep, those are mini brittle starfish. They stay tiny (unlike regular brittle starfish), and help out with detritus. They are good hitch hikers!

[hillbillyreefer]

http://www.nano-reef.com/invertebrates/
http://www.melevsreef.com/id/

I'd bet the two you have are both on the first page of the first link. If not try melevsreef.
Let us know if you need more sites.