Green Slime Algae?

[dlhirst]

I had an almost overnight outbreak of a slimy, dark green algae that seems to generate really large gas bubbles. The bubbles kinda stick to the algae until you disturb them, and only then do they rise to the surface. They have no discernible smell - at least not for me.

Any thoughts on what this is? How'd I get it? And, how do I remove it?

pH = 8.0, N = 0.0, NO3 = 0.25

Today I just scooped out a bunch, it seems to clump up with the aragonite, but I expect it to return...