If you've decided that you must use medication on your tank, Maracyn (a brand name for the anti-biotic Erythromycin) does work for wiping out BGA and many other gram-negative bacteria. Use only half the recommended dose for BGA and it should do the job nicely. It may have side-effects on some plants (Riccia does not seem to like it) and fish so be prepared for them.
And like you've probably already read here and on other forums: using medication will get rid of your BGA, but it will simply reappear if you do not remedy the issues that caused it in the first place. Elevated nutrient levels (NO3
) and high-light without CO2
supplementation are prime drivers for BGA. It also thrives in tanks with poor filtration (read: low O2