I have a 40,000 IG pool. Builders initially forgot to install overflow pipe and with torrential downpours this spring in Texas the pool overfilled for several weeks and the filter quit cycling and had to be cleaned several times before the cartridges were eventually replaced. Needless to say we had an algae explosion. Got that cleared up and have been enjoying the pool ever since.
This AM results:
We have been using chlorine tabs but even those haven't been keeping the chlorine levels up. Currently have blackish mold dots in the shallow end. Guessing the CYA level is so high because the pool company shocked it so much to get it back from the murky depths plus the pool tabs. I don't have any plans on replacing the water as I had it trucked in to the tune of $500/load.
Next plan is to shock with bleach today and tomorrow and turn off the pool tab.
I also have an ozonater but i realize it doesn't do much during the summers here in Texas.