Hi Watermom! Sorry for double post. I do not know the exact amount of CYA last year but remember that according to a test strip everything looked fine. I was using dichlor shock at the beginning of this season as well but again didn't measure any chemistry until water was clear. Thats when I kept noticing 0 chlorine reading even after shocking. I'm leaning towards ammonia now. I'm gonna get an ammonia test and check it out and then do a 2 gallon bucket test with Clorox Is there a certain type of ammonia test I should get?