I don't have a problem with the CC being a signal to allow the Cl to drop off to normal, necessarily, but it can't be used as THE indicator of a need for shocking--I've seen plenty of times when algae is growing but the CC is still zero. Rather, I think it's best to use a combination--if you've shocked to kill an algae bloom, then when CC is zero and your algae is no longer green, then let the Cl fall off. It really depends on the situation.

Janet