Before I SLAM to get rid of the other algae that's plaqued my pool, I want to properly remove the two actual spots of black spot algae. Just wanted to check I'm following the 100% right procedure.
I started yesterday - at first brushed them vigorously which actually made the spot larger (as if some algae was coming out from under the protective membrane) but it also showed where the membrane is. Then I placed a trichlor puck on part of one spot, left it about an hour, took it off and scrubbed it etc. have repeated that today again for a 2 hour period. But I'm noticing it's not really getting less, or if at all only a very very small amount. I suppose the algae has been there for some time so might even take multiple pucks to remove? Most articles mention 15-20 mins but for these that is nowhere near enough, it's looking like I'll need them on each for whole days at a time. I don't have a tool to rub them on it but tried to a bit with the pool pole.
So checking the procedure is ok to just let them set on each algae, then every 2 hours move it and brush more with ssteel brush, then move the pucks back on? Do I need to press down on them with the pole? My CYA is 25 so it wouldn't matter if the few tablets end up adding some to it.
See pics below (first pic is one spot as it's been for months, then after brushing very rigorously has spread more, same with the other side in next two pics).
Appreciate everyone's help here!
Pics - one spot leaving it as is for months:
After vigorously brushing yesterday & up closer, but it's spread in size
Second spot before brushing
second spot after brushing