I converted from Pristine Blue a few weeks back and intially I added 4 lbs of CYA. I added it through the skimmer and waited a week to backwash. At the end of the week and even 10 days out I was still showing no CYA. I bought more and added it to a sock and placed it in front of the jet 2 days ago and I'm already getting a little bit of a reading but still under 30. I added some more tonight in the sock to bring it up a bit more.