Thanks Rick. I’ve been using the card for a week so it’s broken in. My PH is 8.3 so good there. I did a windex vapor test on the card and it reads “toxic” just fine. And when I switch between tap and pond water I give the card 20-30 minutes for the reading to change/adjust. It’s just strange that when I test pond water and then add a healthy dose of SAFE to the small jar, it never goes to yellow or the safe reading.