API Nitrate test accuracy with copper

[mfinn]

I have all my fish in a 90 gallon tank and I am treating with Coppersafe.
I have been testing every other day for copper, but have neglected to test nitrate for and a week.
I tested with the API nitrate test this morning and it reads almost off the charts.
Last test I did the nitrate was in the 10- 20 ppm range. I did a 35% water change with copper treated water, but forgot to re-test for nitrate.
Is this API test kit reasonably accurate with Coppersafe?

 

[Humblefish]

Most likely the presence of copper will throw any liquid test kit readings off - including nitrate. FWIW; nitrate in a fish QT is usually not an issue - unless it were to reach into the hundreds.

 

[mfinn]

Most likely the presence of copper will throw any liquid test kit readings off - including nitrate. FWIW; nitrate in a fish QT is usually not an issue - unless it were to reach into the hundreds.

It was high enough that it made me uncomfortable, so I can imagine what the fish felt. I did a 50% wc today with coppered water. I'll check both tests later and will probably do another 50% tomorrow.