What is this

[mipstien]

This came attached to a clam that I put in early last year. I wasn't sure it was alive until it released and ended up in the sand recently.
It looks like some sort of oyster with the slate looking shell.
I turned on the white lights to get a better picture.

 

[DSC reef]

That's exactly what it is, oyster/bivalve. Non photosynthetic, it filter feeds small particulate from the water column.

 

[mipstien]

I appreciate the fast response!
I suppose it is nothing to worry about. Should I give it any extra phyto when I feed?

 

[DSC reef]

Your welcome. Nothing to worry about at all. Adding some phytoplankton won't hurt, little goes a long way.