Which test kit should I trust

[Timfish]

Do a search for "nitrate calibration standard" if you want to verify how accurate your test kits are.

 

[LxHowler]

Do a search for "nitrate calibration standard" if you want to verify how accurate your test kits are.

Thanks that's actually the sort of thing that I was looking for when I asked this question. I'm happy now with the nyos kit so probably won't be buying any

 

[reefz]

Like said before, hanna checkers are the most reliable. Im fine using the salifert ones if you know how to use it