You can probably by cya at Walmart, Lowe's or Home Depot. It may be called stabilizer or conditioner. Check the ingredients and make sure it says cyanuric or isocyanuric acid. Aim for an initial reading of 30. Put it in the skimmer and then don't retest, redose or backwash for about a week to let it dissolve. If it was me, I would just add the cya outright instead of messing with the frog floater. Until the cya starts dissolving, you'll need to test your chlorine morning and evening and each time add some bleach. After you start to get a reading, you'll be able to just test and dose with bleach in the evenings only.