This has started to take over my frag racks and I noticed it on a few of my rocks. I've got really good circulation across the tank now and feed everyday what the fish can eat. Have been adding reef roids every week once a week. Brown algae...I know what the green is
Looks like a Dino / Diatom problem, cut back on lighting and see if that helps also are you running GFO reactor / carbon or anything? try and run a reactor and cut down on lighting for a few days and see if that helps!
I just had the same problem it looks exactly like mine and it's Dino just cut back on the lighting and I got it also when I would add marine snow to my tank I light my tank for about 5 hours to 6 a day and it's dying off now