Hi - new house with pool last year, and used your method with great success after daring to educate myself about chemicals and earning the nickname "The Chemist" at the now-boycotted pool store. (They got irritated with me when I actually wanted to know the chemical and function of lame-name products like "Water Polish," etc.)
My issue: opened my pool a week ago, much delayed due to ratty weather. Retracting electric cover revealed water in pretty nice condition - could see drain down 5.5 ft, just a few leaves and very fine debris. Started shock process and vacuuming. It just takes so long to get clear - I wind up shocking for two weeks because I don't stop until my water is pretty reasonably clear, and of course, my tests come out OK.
Historically, I have two main pool issues. 1) My fiberglass develops "tea stains", especially after shocking, which respond marvelously to your ascorbic acid advice, and 2) my water takes forever to clear, and is never as bright and sparkling as I remember our pool when I was a kid.
I've read TA isn't something to get too concerned with, but my numbers are WAY high, I think. I've been topping off the pool with water run through our Culligan water softener - thought this would help with mineral staining.
Using the tk test kit, here's the figures:
FC - 8 (it's rained - know I need to get back to 11)
CC - 1.0 (it's rained - tree dirt)
Ph - 7.2
CYA - less than 20 (treated last year, but I use maybe 6 3-in pucks a week for convenience, so figured it would migrate up on its own)
CH - 210
TA - 220
I have a plan to try a little DE in the filter, as so far this year, the pool has never been as clear as before I stirred up all the fine stuff on the bottom after I opened last week.
Do I need to act on this, avoid doing anything, or just wait out the filter? It's been a week and two days - water is basically as clear as when I started (but before I churned up the bottom.)
Thanks so very much for a consult!