So, cleaning off the cartridge filter can make it go away too? The instructions always said to avoid cleaning the filter for 3-5 days after adding the CYA to the pool. I figured by then it would be in your system enough that additional filter cleanings wouldn't make that much of a difference to the ppm.

No wonder we have such a hard time holding stabilizer. Our pool gets a lot of junk in it, so we have to clean the filter quite a bit. We're at 35ppm now, but I just washed the filter yesterday. Is it a good idea to check the CYA after cleaning/backwashing the filter?