Well, I tried a search about CYA and got nowhere (too common or too short, even for just titles) so I just have to ask -- what is it and why would it get so high?

My own CYA is 60 for our 15,000 IG concrete pool, and it worries me because I see the "normal" range is between 30-50. Is there something in particular I should do *now* in order to keep it from going higher?