Thanks Ben.

Looks like I've got a few more items to pick up.

The info I found on the Taylor site referred to the FAS-DPD test using the powder and mention a max test limit of 20ppm:

https://www.taylortechnologies.com/C...P?ContentID=11

.The latest trend among service professionals and a significant number of health officials is testing chlorine with FAS-DPD. This variation of the traditional DPD method allows users to measure both free and combined chlorine levels as low as 0.2 ppm—the maximum allowable level for combined chlorine according to most health authorities as well as the Association of Pool & Spa Professionals (ANSI/APSP)—and as high as 20 ppm. By contrast, the color comparators used with the standard DPD test generally allow readings at the low end of 0.5 and 1 ppm and at the high end of 5 or maybe 10 ppm.
(Bold added)

I'll test again tomorrow morning and see what I get.

Btw, I understand high CL will give false pH readings, so how do I accurately measure pH while shocking? Also you said, vow not to let CYA eating slime grow next winter.... How do I prevent it? Seems like whether or not I lose CYA over the winter has been a crapshoot in the past.....most years no/little loss, a couple times big loss. I don't know what I may or may not be doing that causes this.

Btw, I took a look at what I did at opening last year (I keep records of my pool maintenance) and I added the same amount of bleach, but I didn't test CL until the next day (I got a reading of 16.5). I'm hoping the issue this time is I'm not getting a good reading because CL is over the FAS-DPD test limit, and not that there is so much ammonia that I'm just pouring bleach into a black hole! I should have an answer for this tomorrow.

Oh....forgot to ask.....is it ok to leave CYA at 30 until CL holds? Is this high enough to prevent sunshine from completely depleting CYA?