7enigma... thats the same type of algae i have, and im pretty sure that it is BBA, grows in little "tufts" on my driftwood and around the edges of my leaves. I have read previously that you were doing the dosing that increases phosphates to higher levels, I forget the name of this "experiement". I recently have tried this as well, dosing phosphates to around 2 ppm, and maintaining 20 ppm nitrate. I wonder if this could be the cause.
Maybe the SAE prefer the green algae over the black stuff, so we will see when they run out of green if they head over to the black. Im keeping my fingers crossed because the wood the algae is growing on is pretty much supporting all kinds of rocks and plants in the tank with make shift walls, as well as java moss growing across multiple items including the wood. Taking it out would be detrimental to my aquascaping.
For now I plan on reducing phosphates while increasing CO2 to see if that assists in the dying of this stuff. Its a bear and doesn't come off easily at all. It was growing on the discharge of my bio-wheel water fall, and hot water and my finger nail did the trick, but off of pourous wood, i have no idea how to handle that.