H2O2...treat....with syringe. Target to spray around 180 ml in a single dose. No water movement and let it say for 20-30 minutes. Do large water change. 60-80%. Removal all BBA whatever you can while syphoning water. Give a day or 2 and repeat the same process...3-4 treatment will take care of the algae: Increase Excel to 10 ml after treatment.
"The future's uncertain, and the end is always near."