Low(er) resolution of NO3 test

[Semisonyx]

I’m dosing NaNO3 because NO3 reads zero on my NYOS kit, despite heavy feeding, turning my skimmer way down, and removing most of the macroalgae in my sump. PO4 has climbed to 0.05, but after a few days of dosing 2g of NaNO3 in some tank water to my 180g aquarium, I’m still showing zero.

Would doubling the amount of reagents and dividing the resulting color to number by half give me a half resolution (.5, 1, etc...)?

 

[Semisonyx]

I just finished up running a test using the typical 5mL sample and doubling the reagents. Finally some color!! Looks like it matches 5, so I suppose I’ll divide that by half for a result of 2.5ppm.

Sucks to use 2x the reagents, but man is it easier to discern the color.

 

[Randy Holmes-Farley Verified Community Expert]

I’m dosing NaNO3 because NO3 reads zero on my NYOS kit, despite heavy feeding, turning my skimmer way down, and removing most of the macroalgae in my sump. PO4 has climbed to 0.05, but after a few days of dosing 2g of NaNO3 in some tank water to my 180g aquarium, I’m still showing zero.

Would doubling the amount of reagents and dividing the resulting color to number by half give me a half resolution (.5, 1, etc...)?

No, I do not believe doubling the reagents works like that.

Doubling the thickness of liquid volume you view it through will.

 

[taricha]

That's weird, and not generally true for most test kits.
Most test kits provide reagents in excess so when I doubled the reagents, it didn't produce much of any intensification of color, certainly not linear (2x reagents = 2x color).

NYOS claims 1ppm NO3 detection at the low end, and 2g of NaNO3 in 180 gal means you are adding ~2.1ppm per day of NO3, and it's quite plausible your tank consumes enough to bring it down to 1ppm or below. (Mine does).
Test before, and 1hr after your NO3 addition. If you still see no color, then the test kit may not be working as it ought to.

 

[Semisonyx]

Thanks, guys. I felt like there were some instructions for a phosphate test kit years ago that had some sort of trick to like that it to test on a smaller scale and thought that might have worked for this. I think @Randy Holmes-Farley was right and it was something else along the lines he stated.

I may order a Salifert kit to try out to cross check my nyos results (it’s about time for a new kit anyways).