ID help - white clam shaped growth

[coolastar]

Right in the middle of the picture you can see what I'm talking about. I haven't seen anything like this in all the ID threads I could find. It's about the size of a small grape and opens and closes seemingly at random but not frequently. It also has what looks to be a black thing in the middle. This the underside of a piece of rock that started out as dry rock which has been in the tank since I got into the hobby about 10 months ago. if it's a hitchhiker it must have relocated itself. Anyone have any guesses? Thanks in advance!

 

[blaxsun]

Bump.

 

[Udest]

Brachiopod likely

 

[coolastar]

My caution got the better of me today. I was paranoid it would be some nasty bugger that would spread all over the tank. I turned the rock over for a better angle and pulled it out of the hole it was in. It was stuck in there really well and part of the shell broke as I pulled it out. Anyhow, it definitely does look like a brachiopod - I had never heard of these before! Thank you. I placed it in a darker area of the tank, hopefully it will survive.

 

[Udest]

There's an article somewhere on here about hitch hikers on here somewhere where they have an extensive list of critters , might Wana give that a read will make things much less scary when spotting critters in your tank.

Happy reefing

 

[Uzidaisies]

It was calcareous? Looks squishy.

 

[Udest]

Alot of brachiopods use more calcite instead of argonite to build shells so they're typically more transparent.