we need much much much more information.
What type of light? how much light(wattage)?
Size of tank?
Water parameters?
type of algae?
fertilizer dosing?
2 hours cut back on your light might just not be enough, do you have co2?
DIY co2 really doesn't cut it for 55 gallons...you're probably getting fluctuating CO2 levels which is perfect for algae growth. How many bottles are you running?
when you say p you mean phosphate? i think your phosphate is too high for the conditions that you have. you can 'starve' bba by lowering phosphate cutting back on light (8 hours of 2 wpg should be good).
i agree that your diy co2 fluctuations are going to attribute to this a lot as well.
how often do you do water changes? what % water do you change?