Anybody know this hitchhiker?

[MikeP]

This 'thing?' was stuck to the base of an Acro colony I just bought. Anybody know what it is?

http://i134.photobucket.com/albums/q117/MikeP471612/HitchHikers/8b4fc8bb.jpg

[marie]

some kind of oyster/muscle/ scallop maybe?

[christyf5]

rock scallop/spiny oyster. harmless filter feeder :biggrin:

[MikeP]

Good, thanks! In the sump it goes.