If you have been using the trichlor tabs for a long time, you may have an extremely high CYA level which is a separate issue. People don't realize that the higher their CYA, the higher their chlorine levels must be to keep algae at bay. Take a look at the chart at this link that explains the CYA/Chlorine connection:> http://pool9.net/cl-cya/

You will definitely need to buy a Taylor K2006 or 2006C (better buy) kit if your CYA is high because other kits cannot measure chlorine levels past 5ppm. You can't buy it locally but can get it through this link that will take you to Amazon:> http://pool9.net/tk/

Back to the pH, keep adding Borax, testing and redosing until you get your ph above 7.0. Anywhere 7-8 is fine with mid 7s usually being best for most pools. If you continue to use the trichlor pucks, you'll have to keep a close eye on your pH as it is going to continuously drop due to the acidity of the pucks. It sounds like your ph is way below 7.0 now --- not good. I hope you don't have damage to your pool.

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