I don't think it's bubble algea, but....?

[DaveWF]

I received this piece of live rock with the polyps and xenia (I think?) a while ago. It is heavily purpled, but over the last week or so, I've been seeing these bubbles showing up on it. They're crystal clear - like regular bubbles. They do not appear to be the filmy green bubbles you see on bubble algae. Just, you know... bubbles. FWIW, they're ONLY showing up on this one rock. It's the most aged rock in the tank by far.

Sorry for the out of focus pictures - my camera would only concentrate on the polyp and not anything else :rolleye1:
Any ideas?

http://www.greatcomputerservice.com/pictures/bubbles.jpg

[Aquaman101]

Looks like a layer of cyano on the rock to me. That sometimes develops bubbles on it.

Those front two also look like Aiptasia to me. Check some pics online, but if it's Aiptasia, nuke it now.

[DaveWF]

The guy I got it from told me it was a yellow polyp. Is that possible?
FWIW, it closes up at night and shrinks down to nothing when I mess with it. Aptasia doesn't close up, does it?

[cloak]

The two in the foreground are yellow polyps.

[despot101]

Yeah the front two are yellow polyps, and yeah that just looks like cyano on the rock.

[ghostman]

It seems possible that those are yellow polyps. Aiptasia does close up too when you mess with it. Aiptasia has a browner body, and can get very elongated if it is lacking food. Btw, yellow polyps are not photosynthetic and need to be fed. Looks good so far.