I am new to pools, but I am helping a friend try to get an inground pool (~30,000 gallons) from dark muddy brown to clear.
I was doing pretty good too. Last week it was black; I cleared out all the leaves, added lots of chlorine, floc and did lots of vacuuming. This morning it was pretty darn clear water.

I tested the water and balanced the pH, alkalinity and brought the chlorine up to a suitable range.
This afternoon however, I noticed that the walls still had a grimy film on them that didn't come off with the vacuum. So, I brushed the walls, hoping to losen the junk. When I came back in a couple of hours, the entire pool was muddy brown again! What happened?! Will it go away? What should I do? Help!