So I have a question for TF-100 users. The CYA test directions say to check the mark once you cannot longer see the black dot. Based on this instructions my CYA levels are around 30-40 PPM. However, based on the stabilizer dosage I added to the water and the pool store test results my CYA should be around 80 PPM. I google CYA test and watched a video on your tube of someone who appears to use the TF-100 CYA test and his directions are bit different and call for when the black dot almost disappear. I know per the TF-100 CYA test directions this is a subjective test. Can anyone shed some light on this test, as I want to ensure my CYA readings are accurate to keep the correct FC levels. Currently my FC level is 9PPM, which is a bit hight if my CYA is 80 PPM, but extremely high if my CYA level is 30-40 PPM. Is there a more accurate and less subjective test? I do no trust the pool stores, as I took the same sample to two different stores and one tested my CYA levels at 30 PPM and the other a 70PPM....It's crazy..I do not know what to trust now.