Getting frustrated. Background 20,000 gallon salt water fiberglass pool covered. I've got it pretty good, ph 7.5, hardness 300, cyn 35 BUT Alkalinity 150. So I tried to lower alkalinity by adding muriatic acid. Then upping the ph. I was using sodium carbonate but was told by local store it would also raise alkilinty at the same rate so switched to soda ash. More muriatic acid and alkalinity got down to 100 and ph 6.8. So in with soda ash.
Now ph back to 7.4 but alkalinity back up to about 180.
I'm at a loss as to how to lower alkalinity to get it in line with ph.