Let me share my experience with brown algae. mine too, covered the gravel, the leaves of my plastic plants, and every rock in the 37 gallon aquarium.
In the beginning, I had a 20watt light on the tank. I heard the low light cause thing, and decided to give a lighting upgrade a shot. I went and got a 65w/130w compact flourescent light (runs at either setting). Very nice light, BUT, the brown algae bloomed like crazy even with the super bright lights. I did notice however, there was some green algae mixed in with the brown now with the brighter light.
I added a super big ruffle swordplant, because I also read that perhaps a live plant would outcompete the brown algae for nutrients. But once again, no such luck, and the brown algae actually grew on the leaves of the swordplant... besides, my barbs are quickly making a meal of the swordplant, but that's another story
come phase three... I got a cuckoo catfish, and a redtail shark one day while at the LFS... both of them love to eat this brown algae. they eat all day, all night. and have cleared up most of it.
with the help of these two fish, and stirring up the gravel a little when i vacuum and do water changes, along with scraping any algae off the glass, i've been able to control it to some extent. it's still there, still coming back, but kinda under control.
My hunch is it's got something to do with my tap water, perhaps silicates like SMB has said. But as long as the brown algae isn't bad for the water quality, it doesn't look so bad now that it's semi under control. it gives a pretty natural looking quality to everything in the tank!
- kip
