I think I've heard of something that removes brown algae from the water. It's pretty bad on the plants in my betta tank, and I don't really know what to do for it. I can put my random oto in there I guess because he's solo anyways, but I would rather buy something to do it.
I use Seachem Phosguard and I no longer have ANY brown algae. Depending on how high your phosphates and silicates are will determine how often it has to be replaced in your filter. You will want to get a phosphate test.
Is it a new tank? If its not in your water supply then it usually goes away on its own after awhile.