What is living in my sun coral?

[Cope]

Here are some picks. In the first one it looks like a vertical clam.
I know is a blurry pick, but it's the best I could do.
Under the vertical clam you can see a horizontal one.

Here it looks like a red mouth. The mouth is light sensitive and will retract into the skeleton when hit with light.

Here you can see it partly retracted in to the hole. I believe this thing has caused the hole, not just moved in to it.

Any ideas?

Thanks for looking.
Cope

 

[Homereef]

It is some type or boring bivalve. Usually harmless but can let in pathogens to the core of the skeleton, I would leave it be.

They are very common on waltsmith maricultured sps as well as barnacles.