So do to my own fault I let my FC get low and I stopped using a weekly dose of Polyquat 60 for a few weeks and I have a few small spots of black algae again. I have a couple of questions please and I would appreciate your help. I have a plaster pool in FL, I own a wire brush and I've shocked the pool to 50ppm.
1. Can I use a high dose of Polyquat 60 and shock the pool at the same time.
2. Why black algae?? I would much prefer green algae but it seems like when I screw up I have this beautiful clear water and black algae. Why?