I recently installed a 415 gallon jacuzzi and need to increase my cya. I had bought 2 boxes of this product http://www.lesliespool.com/Home/Pool-Chemicals/Pool-Shock/14543.htmlbefore I found this place and haven't used it since. but was thinking if it had cya and I could figure out the right dosage but... maybe just throw it away and go buy some stabilizer.