Isn't the shock n' swim dichlor? or is it cal-hypo?

At any rate, you can't depend on a test strip to give you a CYA reading, so really the only thing you can do is keep the chlorine in the dark yellow range of your tester, brush the pool as often as you can with chlorine additions, and keep the filter running. It takes time, chlorine, and patience--patience often being the hardest part of them all.

Janet