Our pool is ~24,000 gallons, 6 lbs should have raised the CYA about 30ppm. I know the CYA is in the pool and it is my understanding that the only way to lower or remove it is to drain the water. The pool store read 0 ppm on 3 separate water samples weeks apart, once before and twice after I had added the stabilizer. They claim that my extremely high phosphates are masking the CYA test. Is this possible?

I plan on having another pool store test my water for CYA. I would be testing myself as I usually do but I am out of the CYA regent.