Odd bubble on blasto colony

[impur]

I've had this red blasto since Feb. 2005. It has grown from 4 polyps to this. As it began to spread, i noticed this odd bubble. It has been there for at least a year so i'm not worried about it effecting the colony. I'm just curious as to why its there. To me it looks like just some of the flesh that connects the polyps that isn't really attached to the skeleton. What do you think?

2/21/05

4/26/06

 

[impur]

Anyone?

 

[DonavonsReef]

looks like an Air pocket trapped under the tissue.

 

[impur]

Well it inflates and deflates with the polyps. So if my shrimp runs across the colony, they retract and the bubble goes away so i don't think its air.