I had a type of black spot algae all over my tank, which was definitely different than GSA. It mostly grew on the edge of plant leaves, mainly my anubias and Green Temple Narrow (Hygro Corombosa). I added more phosphates (with New York City tap water, which is high in phosphates), Flourish excel, nerite snails, and otos. I'm not sure which one of those did it, but now the black spot algae is gone.
I've had a bristlenose pleco in the tank for awhile, and he did not get rid of either type of algae. Although its a 75 gallon tank and he grew very quickly, so maybe he just had more than he could handle.