The acid that you add to lower your pH isn't the same as CYA--the CYA is going to come in a package labeled "conditioner" or "stabilizer" or "balancer", but the active ingredient is cyanuric (or isocyanuric) acid. Once you add it via the skimmer, make sure you don't backwash or retest for a week or so because it takes a VERY long time to dissolve.

Janet