I forget the name, but there is some stuff that is basically granules of hydrogen peroxide that has been used successfully to clear ponds. You should read about it a lot more before trying it though... basically you spread it onto the algae and it bubbles like crazy and burns it. Granted, if it lands on the plants, it'll burn through them too. And it's not always good for your fish... thus the need for research...
I assume your plants must be potted? Because otherwise it would be a problem to have no nitrates and no phosphates... Generally you want some of both, in a 20:1 ratio in ppm I believe... I know I dose Potassium Nitrate and Monopotassium Phosphate at approximately 4:1 by powdered volume in my tanks. With the exception of BBA, most other algaes are a sign of nutrient surplus and/or imbalance. I don't know what triggers BBA unfortunately.