When I had some brown algae in my tank, a bought a few otocinclus catfish and they loved the stuff! They had it under control after a few days - including what was on the rocks, gravel, glass, plants, and decorations. You don't need too many to do the job. When they have eaten all the brown algae, however, you have to supplement their diet with algae tablets.
They are cute little guys that may hide on you during the day, but can sometimes be seen sitting on a rock or a plant leaf. They seem to do most of their algae eating at night, at least for me.
Kind Regards,
LogJam