My numbers are currentlyTc 5
Scale build up on this 10 yearold pool is also what I'm dealing with. Not too bad now its just above water line and I got it all off with 220 wet sandpaper.
A member posted this advice Re scale
"To avoid it in the future maintain your CSI slightly negative, -0.1 to -0.3. I had issues with scale on the waterline tile a couple of years ago and it hasn't been back since. Enter all your numbers in Poolmath and it will give you a CSI score. Tweak PH, TA and CH to adjust it. If your PH tends to rise then keep your TA lower (60-80) to help slow the rise. "
Also water quality is almost clear crystal but not 100% I plan on deep cleaning the sand filter and if that doesn't do it then researching here about fading DE to it?