As Caryl suggested, some plants, even just some java fern or java moss, would out-compete the algae for nutrients and prevent it growing. I never had a problem with Brown algae before I set up my rock-only cichlid tank, because all my other tanks are planted, but I put some moss in it a couple of weeks ago and the algae has noticibily gone down, not entirely disappeared but it's definately not as noticable as before.