What is this coral and why is there a bubble?

[mccusker1818]

I bought this at ReefStock Denver last year, it didn't always have the bubble except maybe the last month or so. Any ideas what it is?

 

[nkyreef]

Rhodactis mushroom. Can't explain the bubble. On occasion my yumas will grow them but don't know why.

 

[i cant think]

I bought this at ReefStock Denver last year, it didn't always have the bubble except maybe the last month or so. Any ideas what it is?

It seems to be a Rhodactis as said above.
The bubbles are common in the Rhodactis genus when kept correctly. The mystery behind why Mushrooms like Ricordea and Rhodactis bubble up isn’t known completely however theories are out there with it being a lot of light or maybe a lot of flow.
If the bubble is somewhat more like this and not in the actual base of the mushroom, I wouldn’t worry about it. In the photo it’s hard to tell if it’s the base of the mushroom or just one ‘tentacle’ from the mushroom.

 

[mccusker1818]

It's not a mushroom, it's an LPS. It has a skeleton. Sorry posted to the wrong board.