Dosing Sodium Nitrate and getting a higher reading than anticipated

[Siberwulf]

Good morning!

I put in a trial dose of Sodium Nitrate (from Amazon) following the guide here: http://www.theplantedtank.co.uk/calculator.htm

Based on the 90g tank, and 1lb (454g) in 4L of water, I should have seen a bump from 0.0 (yuck) to 1.02. When I measured NO3 30 minutes later, it was reading 1.6.

Is this a significant problem, or is that within normal ranges?

 

[Randy Holmes-Farley]

Water volume estimates, test kit uncertainty and liquid volume measurement uncertainty likely all contribute.