I know that some anti-bacterial medications work well, but can't remember which ones exactly. Also they might harm your nitrifying bacteria, so if you have a lot of fish in the tank it's not recommended. Also, increasing the current should help, as BGA thrives in stagnant water. I remember reading somewhere that increasing nitrates helps too, but I'm not sure if this is true.
Every time I increase the flow, the algae starts getting these long strings of algae shooting off of it. They seem to release some sort of seed too. The seeds look like the little string fibers that you get if you start rubbing a paper napkin on dry glass. There are lots of them too.
So macryn seem to have done the trick for you, then?