get a SAE, and I have had a lot of succes, after fixing my fluctuating co2 problem by overdosing flourish excel, recomended dose every morning instead of everyother day.
I've just had sucess destroying this type of algae by spot dosing the affected area with excel in a syringe (just a cheap one from your local supermarket works fine). Within a few days it will turn gray/white and soon after it will be gone. To avoid BBA in the future, invest in a pressurized CO2 system.