What to be or not to be

[reefthereefer]

Can someone tell me what this is I spotted it in my tank attached to a rock close to the sand bed about a month ago my wife pointed it out I thought it was part of the Rock but yesterday I noticed it closed up real quick and would open almost like a Venus flytrap so today I finally was able to grab it and pull it out and this is what it looks like

 

[bobnicaragua]

Why pull it out?

 

[kevgib67]

I don’t recognize it but my bet would be a type of bivalve, filter feeder. Nice addition, though I don’t know how well they do in our tanks.

 

[ISpeakForTheSeas]

That's a bivalve (taxonomic class Bivalvia; it contains animals like clams, mussels, oysters, etc.) of some variety - it's a harmless filter feeder and a neat find.

 

[reefthereefer]

Why pull it out?

I didn't know what it was I thought it was something bad