In a 30,000 gallon pool with ph who knows how far below 7.0, I'd start with a whole box of Borax. See what that does for you. When the ph starts to rise, you can then begin to adjust your doses depending how how much change you are seeing. It may take a lot of Borax if you are really, really low -- especially in a pool that big. Wait 4 or 5 hours after each addition and then retest.