I have been fighting some bad BGA for weeks, finally broke down and got some maracyn. Used 1/2 of the package dosing and within 24 hours my tank looked a zillion times better. On day 3 of treatment now and it's all but gone. Also keeping a close eye on my nitrates and phospahtes trying to get them up to a reasoanlbe level, and man all my plants are looking wonderful now, and even seeing soem new growth.
DF's right...90% of the time increased water movement stunts BGA...the other 10% of the time it's un-phazed by it. That' the same issue I have..mayca and rotala indica growing BGA, and both are right under the HOB 'waterfall'.
I'm starting the marycin tonight....*sigh*