False Nitrate reading?

[tram]

Hi
Im doing a fishless cycling at the moment using Dr Tims 1 and only, the first water test after dosing ammonium chloride, the Nitrate level was 100 and still is after day 8/9, during this time I have also had a reading for nitrite from 1.0 on day 2 to 0.25 today. I have come across a few statements in forum answers that say that the Nitrate result is false if there are Nitrites present in the water.

Is this true? should I only be concerned about the Nitrate result when Nitrite=0.

Using Salifert test kits.

Tony

 

[cracker]

I'd like to know as well as I'm cycling a QT & my tests seem off. Here's a bump !

 

[pandagobyguy]

This just seems like your tank is finishing the cycle. Once your nitrites read zero, do a water change (a huge one), make sure your nitrates are at or below 5 ppm and you are ready to add your first fish.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, the Salifert kit will read false high nitrate in the presence of nitrite, at least last time I heard it from Habib Sekha, owner of Salifert.

 

[Christoph]

Hi,

every nitrate test that develops the pinkish color for comparison will give a false high reading for nitrate in the presence of nitrite. The factor depends on the testkit but is at least 10x-100x.

The reason for this is, that the nitrate tests work indirectly by first reducing nitrate to nitrite. The formed nitrite is then reacted into the pink dye (an diazo coupling for the chemical minded).

In an experiment i conducted with the salifert kit 0.2 mg/l of nitrite gave a reading of 4.1 mg/l nitrate. Find attached also a kinetic study for color comparison using the salifert test (but others use similar chemistry) with a 10 mg/l nitrate sample and with a 10mg/l + 0.2mg/l nitrite sample (sorry, only in german, x-axis: time in minutes, y-axis: color intensity measured as absorption @530 nm).

Best,
Christoph

 

[tram]

Thanks for that. I shall wait until nitrite is zero before I test for nitrate. I may not have such a massive crisis after all

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for that. I shall wait until nitrite is zero before I test for nitrate. I may not have such a massive crisis after all

Sounds good.

Happy Reefing.

 

[Randy Holmes-Farley Verified Community Expert]

Hi,

every nitrate test that develops the pinkish color for comparison will give a false high reading for nitrate in the presence of nitrite. The factor depends on the testkit but is at least 10x-100x.

The reason for this is, that the nitrate tests work indirectly by first reducing nitrate to nitrite. The formed nitrite is then reacted into the pink dye (an diazo coupling for the chemical minded).

In an experiment i conducted with the salifert kit 0.2 mg/l of nitrite gave a reading of 4.1 mg/l nitrate. Find attached also a kinetic study for color comparison using the salifert test (but others use similar chemistry) with a 10 mg/l nitrate sample and with a 10mg/l + 0.2mg/l nitrite sample (sorry, only in german, x-axis: time in minutes, y-axis: color intensity measured as absorption @530 nm).

Best,
Christoph

Thanks for the data!

 

[tram]

Just an update. Today my water test finally showed a nitrite =0. So I tested nitrate and this gave a reading of 25ppm. So a positive nitrite reading did give a false nitrate figure in the salifert test kit.
Thanks Christoph & Randy
Time for some livestock

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the update.

Happy Reefing.

 

[nosmok]

Why would my Salifert nitrate test consistently read high (50-100 ppm) when my iDip, Api and Red Sea test read below 10 ppm? This is a well established tank > 1 year.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t know why or which, if any, are accurate. Reef testing is a frustrating enterprise.

 

[loz]

Why would my Salifert nitrate test consistently read high (50-100 ppm) when my iDip, Api and Red Sea test read below 10 ppm? This is a well established tank > 1 year.

My Salifert nitrate test also read high 50 to 100 even i did 50% wc still read the same

 

[nosmok]

My Salifert nitrate test also read high 50 to 100 even i did 50% wc still read the same

I had the same experience! Dropped to 25 ppm for a few days, then back to 50ppm. Funny thing was that I changed to Salifert after I had a bad API reagent give me false LOW tests. Having built a Triton sump with a large refugium with a dedicated SBreeflite Sprite fuge light, a biopellet reactor and Biospheres chasing those nitrates levels, I have a healthy skepticism for single platform test kits

 

[Randy Holmes-Farley Verified Community Expert]

In general, most nitrate kits can barely read a factor of 2, so you might hardly detect a 50% water change anyway.

 

[SteveC]

I am trying to find out if the salifert nitrite test may show a false reading in the presence of high nitrate e.g 100+ .

I understand the reason the other way around.

 

[Reefman71]

Hi,

every nitrate test that develops the pinkish color for comparison will give a false high reading for nitrate in the presence of nitrite. The factor depends on the testkit but is at least 10x-100x.

The reason for this is, that the nitrate tests work indirectly by first reducing nitrate to nitrite. The formed nitrite is then reacted into the pink dye (an diazo coupling for the chemical minded).

In an experiment i conducted with the salifert kit 0.2 mg/l of nitrite gave a reading of 4.1 mg/l nitrate. Find attached also a kinetic study for color comparison using the salifert test (but others use similar chemistry) with a 10 mg/l nitrate sample and with a 10mg/l + 0.2mg/l nitrite sample (sorry, only in german, x-axis: time in minutes, y-axis: color intensity measured as absorption @530 nm).

Best,
Christoph

 

[Reefman71]

This is my NYOS nitrate kit. Now I know why I could not get a reading, I’m cycling my tank and still showing high Nitrite. That explains it, thank you!