What kind of lights are you using and how far away from the surface of the water? Since you said you dose dry ferts and you have BBA problems, I would check in on your levels of co2 and amount of fert dosage. I believe BBA is a nutrient starved algae so increasing you micro nutrients will help. Co2 will help a lot if you do not already have it. 30ppm of co2 will usually kill it. Or you could also dose metricide or spot treat it with hydrogen peroxide.