If the CC were from chlorine combined with organics in dead algae, then a floc could have settled them to the bottom so that CC isn't registered anymore. That seems plausible. Normally this sort of reduction occurs when the algae gets removed by filtration but obviously that wasn't working in this case.

Just so we know and can keep track of these things, what brand (name and manufacturer) of floc was used? I've heard of good results with OMNI Liquid Floc Plus for a flocculant and have personal experience with GLB Clear Blue for a clarifier.