He can run high cl levels to compensate for the high cya (but he'll have to be extremely diligent about keeping the cl level between 8-15 ALL the time) or he can do a partial drain. Either way will work. If it were me, I'd do a partial drain, though.

EDIT -- as soon as I posted, I saw that you had also posted while I was typing. If he doesn't want to drain, it's ok. But, he MUST not let cl drop below 8 ever or he is gonna have big algae problems. Hope this helps.