Stock tank pool for dog rehab

[bcaddict]

I use a 350 gal Rubbermaid stock tank to swim my dogs. The pump/filter is an Intex 800gph model 635. I clean/replace the filter twice a week. The pool is brushed daily and skimmed a couple of times a day if not covered. I've used bleach, dry acid and flocculant when needed. I uncover the pool when it rains and add fresh water when the level subsides. I've just opened the pool and added flocculant for the fine dirt on the bottom. I've brushed it to agitate and later turned on the pump. The pump runs 8 hours a day. Now everything is off the chart high except the pH. It's around 7.0. I am desperately trying to avoid having to drain the tank. Since I've opened it I've added about 10% fresh water. Could I have skewed the dissolved solids level by adding too much flocculant? Unfortunately the water here in Tucson starts as hard water.
TC =10ppm
FC=10ppm
TA=~140ppm
pH=7.0
TH= between 500 and 1000