after adding 1.5L of Phosfree 48 hours ago, the AquaCheck test shows about 100 ppm (definitely a bluish tint, but not matching the 200 ppm color). the Natural Chemistry test still shows greater than 1000 ppm.

yesterday, I checked on the pool at 11 am and at 3 pm. there was visibly more of the brownish powder in the shallow end.

It accumulates in the same patterns every time. could it just be a particulate and not living algae? I don't understand where it is coming from if its dead algae. I really don't understand how it could double the visible amount in the course of 4 hours if it was growing.

the powder isnt attached to the floor and it brushes away with movement, but there will be obvious green growth under the powder (sometimes).

Saturday at 8 am there was very little material in the pool and the OTO test showed 10 ppm. Sunday at 3 pm the OTO test was maybe 4 ppm.

I am thinking about increasing my regular FC amount to 6 ppm. previous years I have just been around 3 ppm, but the CYA from test strips was less than 30. 10 ppm seems to be the breaking point for algae growth (not the brown powder, but greenish tint to the water and green algae on the sides and ladder).