I frequently get light algae on some of the walls and nooks and crannies when I neglect the pool for any period of time. Brushing those areas is tough. I rig the vacuum hose and brush to one of the return jets so it blows. Makes it easy knock stuff loose. Typical return jets are 1.5" threads so just get a 1.5 inch male PVC pipe adapter and cement a short piece of 1.5" pipe in it. The vacuum hose end that hooks to the skimmer will fit inside the pipe. Also get 1.5 inch threaded pipe plugs for the extra return jets. Take out the eyeball, screw this thing in and go. Once the algae is in suspension the chlorine can do its job easier. Never had to deal with black algae but this may help.
Al