Well I either have a dud test kit or API sucks, lol. I have a Salifert NO3 test kit but had lost the colour reference chart so I hadn't tried it. API has always said 0.
So a question for you other API testers: Do you look through the vial top down or through the side????
I also found a ELOS NO3 kit tucked in behind a bunch of other stuff as I was setting up my QT for my wrasses coming in tonight. And it turned out I was using the back of the Salifert colour chart for my Hanna phosphate reagent funnel
Both the Elos and Salifert tested around 100ppm NO3 in my cycling 210 gal tank. API (looking through the side of the vial) still says 0
So, water change is going to happen today or tomorrow and we'll see where we stand...