What chlorine level to shock -- now that half my CYA is gone

[JimK]

Ammonia would react almost instantly with the chlorine.

Richard was mostly (I think) referring to other compounds which react much more slowly.

That probably explains where all the CL went after the first shock; I put in 5 gallons of 8% and when I tested the water about an hour later FC was 0 and CC was .5

I'll post how the filter CL demand test goes.