Hi Big Dave- THANK YOU for an explanation that makes sense. The only caveat is that ( and I'm being honest here) I forgot about the mineral sanitizer until I looked through my pool papers, so I have not ever changed the cartridge in 2 1/2 seasons of use. So I wonder if it's still doing anything.

Staining wouldn't be good, but I wondered if I could do a stain test while adding the bleach at intervals. I'm assuming you don't add 6 jugs at once?
Oh- last night at around 10:00 I went ahead and did add 1 jug of bleach, very very slowly to see what would happen. 2 hours later I tested the water, then closed the cover.

Last nights results (around midnight): FC=3.5. CC=1.0
This morning I opens the pool around 10:00 and tested again: FC=1.0. CC=.5

I will start my test bucket, and wait for more info on how much bleach to add.
Thank you !!!