Need help id'ing

[habs247]

I again turn to the experts.

For the past couple of days I have been proudly thinking that I am starting to develop coraline algae on my base rock rock. Purpleish spots have begun to appear on some spots on the rock which had me convinced.

Uhh not so fast newbie.

Today I noticed that one of the more advanced spots is actually looking fuzzy, so that's not the kind of algae I want, I'm guessing.

Question is, what is it? Cyanobacteria? It does not appear anywhere in the sand bed, just on the tops of several rocks. This particular spot, which it seems more advanced, and therefore has become "fuzzy", is actually in a lower flow area in the corner of the aquarium.

Help!