Brown algea on live rock..

[wembleey]

I had purchased live rock put it in my tank, it was really pretty a week later its brown. I know about the whole light and water = algea I don't leave my light on for more than 12 hours. I just don't like how it looks, its also on my sand bed. Is it my lighting don't have special marine lighting. Is this normal I don't want my live rock looking the way it looks right now. Any help would be cool!
Thanks Nikki

 

[criminal]

cut back on lighting a couple hours and it's die off from the microscopic critters that live in the rocks, very common in new tanks. do you have any powerheads? it keeps the die off from settling down on the rocks or sand and keeps it in circulation.
Matt