Definitely BBA. How long do you run your lights daily? What is your nitrate level? How often do you do WC
's and how much do you change out each time?
Until you get the algae under control only run lights 6 hours daily. Once the algae is gone and the problem that caused it is corrected you can slowly build up your time by 30 mintues every 3 weeks or so until you see algae begin to form. Then back the lights down 30 minutes and this should give you the amount of time you can run your tank daily without having algae issues.
In the mean time you can spot treat the algae using hydrogen peroxide 3%. Turn off your filter, pull up 1-3ml of peroxide for every gallon of tank water in a syringe, hold syringe right up to algae and slowly squirt. Leave filters off 20 minutes. If you have a lot of algae you will have to spot treat an area each day. But remember if you don't correct the problem that caused the algae in the first place it will return after spot treating. Also usually within 24 hours the BBA will begin turning white, pink, or red which means it dying.