Not sure what to do about this nuisance algae?

Got a 125 gallon saltwater aquarium. Have had it cycling aver a month now, I put 2 damsels in there about 2 to 3 weeks ago and they are doing great. All of my water checks are perfect, 8.2 PH, 0 ammonia, 0 nitrites and basically 0 nitrate. Salinity is perfect as well. I was just about to add a couple more fish when all the sudden brown algae started covering my Live rock. I read about what they call a 'brown out' that is normal but it is supposedly supposed to "disappear as quickly as it showed up" going on a week now and it only got worse, not only is it on the rocks, its all over my live sand as well. note my water check are all still perfect. What is wrong and what do I do to get it to go away? It looks kind of cool on the rock but I want it off my sand!!! Any suggestions?