So things have been going fine all season, I test FC & PH regularly, only use liquid chlorine (I have done great with the Wal-Mart pool essential), test TA & CH periodically and everything been great. I decided to test CYA this weekend and I am getting no reading, meaning its below 20????? My chlorine does not appear to be getting used up abnormally fast, what is going on? What should I do? As always, thank you in advance for your help!