I have been using diclor in my pool for the last year and have just used a load of it to shock my pool. Until now, I didn't realize it had CYA in it. Now I'm worried that my CYA levels are through the roof and I have been reading that this could make my chlorine ineffective. I can't get hold of a CYA test kit at the moment as the shops are all closed due to the pandemic. Until I can get hold of one, I'll use unstablized chlorine. My question is: if my CYA levels are too high, how do I know if my chlorine is effective? Is it possible to have a FC reading but that chlorine still not be effective at killing germs?