25 year old pool PH 6.2 OR LOWER

I NEED HELP: 20,000 GAL. pool pebblebrite, PH 6.2 or lower, TA 125, CA 125, TDS 1980, HARDNESS 1000, tried adjusting PH with PH UP, of course TA went up and PH did nothing, search internet and found your POOLFORUM, and the article on Borax, thought I found the answer, 2lb borax in pool waited 2 hours tested and found my borate level is at 80 tested again 24 hrs. later still 80, also aerated the pool 24 hrs., TA did drop 15 pts. now 110. TWELVE years ago I tried Borax with no luck, the info was nothing like you have on your site now. The 2lb of borax did nothing to increase PH, and I did not expect much if any change. My question is why does my borate read 80 and with that reading how will I change my PH. The test strips for borate are Aquacheck, I have ordered the LaMotte strips though, they should be here on 26th. Could the high hardness be the problem. All test were done with liquid test kit except for hardness it was done with test strip. In rainy season now algae problem will get worse, very bad now.