Ugly algae ID

Sorry if this ID is redundant but i checked the stickies and it doesnt seem to be on there - at least not in the first page. My tank has just completed a little mini-cycle with LS(no rock yet) and ive been running the lights 10 hrs a day for about a week; for the last 3 or so days ive had some brown splotches of algae growing on my sand. Not sure if its good or bad but it certainly is ugly....its strange stuff it spits out tiny little air bubbles every few seconds making it look like i have a little airstone in there or something. Anyway i googled it and can't find any definate answers that im satisfied with so im turning to you guys!!! Heres some pics:



Sorry about the poor quality but i think you get the idea. Thanks!

 

cyno or diatoms

 

harmful?

 

they will go away with time, but if you add rock down the road they will most likely reappear. not harmfull, most of the time, cyno can and will blanket everything if not controlled. new tanks and poor water conditions are the source.

 

i dont really think its cyno....i googled cyno and the stuff i got isnt remotely hairy and its tannish brown- not much red in there like cyno seems to be- i think its most likely diatom but im puzzled as to why bubbles come from it?