The pool is an above ground 21,000 gallon capacity. It is a Pentaire single cartridge filter unit. Started with algaecide , soda ash, tons of leslies pool shock , conditioner, flock, phosfree, and on and on. I just started using regular bleach 4gallons on sunday and for the first time I have a reading which is very high. My ph was low so added Borax and it is about 6.8 . My alkalinity is very high 240. Cyanuric acid is 0. I have been using test strips.