I'm not sure if that is bubble algae I'd get a few emerald crabs and hermits. I wouldn't brush it off. I've read that by breaking it up like that you can release spores which will only make it spread. Not sure how true it is but it's at least worth looking into.
I had bubble algae and it was green bubbles looked like tiny underwater balloons. The crabs took care of it.
Also as above post stated. Check your phosphates.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley