Re: Is this BBA?
That sounds like BBA, and if you remove the infected leaves, or kill the algae on them with peroxide or a bleach solution (the last two are not universally accepted practice), and raise the CO2 level it should be gone for good. I have done that, but I still get tiny patches of it on my heater, which is in the direct path of my CO2 mist. Algae likes all the same "food groups" as plants.