yes, CYA = Cyanuric Acid, aka "stabilizer"

Here's a copy of the "Best Guess Table" that we use as a guide around here...
Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

So with a CYA of 30, you have to get your Cl up to 15 to even achieve a shock level. You probably could to go 20-25 without any problems but I wouldn't go any higher than that just to be on the safe side, unless you increase your CYA level. Realistically, though, anything over 15-20 for a CYA of 30 is overkill anyway.

If you still have green water, then you need to raise your Cl to 15 ppm and keep it there by testing and adding more 2-3 x daily in order to consistently maintain 15 ppm. When your water turns blue/cloudy, then you can let the chlorine drift back down into the 3-5 ppm range and your filter will take out the dead algae.


Janet