I just spent a couple of hours swimming in the pool scrubbing black algae off the walls using a trichlor puck and a SS brush. I managed to get a lot of it to break off wherever it was protruding from the wall, but there is a lot remaining. Lots of pits and grooves in the plaster (~ 25 yrs old).
I'm pretty positive it is black algae. The spots are round, and they smeared dark green when rubbing off.
What should be my shock level to try to get rid of this black algae from ****? I have a bottle of Polyquat 60. Will that help? I read it can help break down the chlorine resistant parts of the algae.
Borates : hopefully 50ish, added yesterday, didn't try test strip yet.
Besides the black spots, the water looks better than ever.