Hi Les,

I have a 24' round also and it took me about 5 lbs of CYA to get to a level of 30 (although I had a lot of rain and had to drain water out of the pool on several occasions).

According to the BleachCalc program, it should take 3lbs and 3 oz to bring the CYA up by 30 ppm for 13500 gallons. I usually wait at least 5 full days to test but it looks like you could add at least another 1/2 lb while you're waiting. Retest in 3 days and you should see something by then.

Peter