Hey new to forum, had pool for 10 plus years.
About 3 years ago we switched from chlorine to an ionizer system with copper bars and electricity for the sanitizer. I have developed brown spots on the bottom of the pool opposite of the water flowing into the pool.
I have tried the vitamin c test on the pool bottom and it did nothing to it. I have put a chlorine tablet on the and it lighted the only to come back.
My numbers are as follows.
Copper .5 ppm
p.h. 7.3 ppm
total alkalinity 110 ppm
Calcium Hardness 220 ppm
TDS 2000 ppm
Please see the attached picture