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

[chem geek]

Yes, that's correct. In my situation, given the eventual chlorine demand and the amount of CYA loss I should have seen (if ammonia were present) very high CC levels over 30 ppm before it would have started to drop again, but in fact I only saw it rise to no more than 1.6 ppm CC. So the bulk of what was in the water was something other than ammonia, but that the chlorine reacts with albeit more slowly. I guessed that it was the intermediate breakdown products of CYA -- basically the bacteria weren't finished eating it when I got to them. We've seen other reports where the CC is high after adding chlorine and gets reduced rather easily and quickly, albeit needing lots of chlorine. For CYA degradation, it basically goes through the following steps so depending on where it stops you can end up with a mixture of different chemicals that will behave in different ways and you can get a mixture of any of the following:

CYA ---> Biuret ---> Allophanate ---> Ammonia ---> Nitrite ---> Nitrate
.................................................. ......... | .............. | .............. |
.................................................. ......... | ....... Nitric Oxide ... Nitrite
.................................................. ......... | .............. | .............. |
.................................................. ......... | ..... Nitrous Oxide ...... |
.................................................. ......... | .............. | .............. |
.................................................. ......... `------------`-------------`---> Nitrogen Gas

The following table shows the speed of chlorine demand for each chemical and whether it forms significant CC:

Chemical . Chlorine Demand . Forms CC
CYA .............. Very Slow .............. No
Biuret ............... Slow ................. No
Allophanate ....... Slow ................. No
Ammonia ....... Very Fast .............. Yes
Nitrite ............... Fast ................. No
Nitrate .............. None ................ No
Nitric Oxide ....... Fast? ................ Yes?
Nitrous Oxide ..... None? .............. No?
Nitrogen Gas ..... None ................ No