API tap water conditioner and nitrite false positive?

[AJ356]

A long post just to say..... I'm getting false positive nitrite readings when using API tap water conditioner. Has anyone had this, or heard about it? You might not care to read the essay below!

The extra detail is for any geeks who want to help do a deeper dive. Or the deeper dive is probably "Well, API tap water conditioner causes false positive nitrite readings, end of". But I am also wondering if there is any "real nitrite" in the water once you add the conditioner? And if this is even scientifically possible?

I also can't get a straight answer as to how long API tap water condition remains "active" in just water. I already know the ingredients are sodium thiosulfate (presumably to separate the chloramine/chlorine bond and neutralise the chlorine) and EDTA tetrasodium salt (which I think neutralises the heavy metals in tap water).

I've been using test kits for years. I am one of these people who loves this part of the hobby. Mostly I use API kits, but I have experience with other brands. Currently, I have no reason to doubt my API nitrite test kit. It's quite new and behaving normally with all my set up's when tested, and my tap water.

I get detectable nitrite readings in my tap water about 90% of the times I test it, always have done. It varies between barely registering such as about 0.1 ppm, to measuring pretty bang on to 0.25ppm or just below. Mostly, thankfully, it's much closer to the 0.1ppm range. I know the API chart goes from 0 to 0.25ppm with nothing in-between.

Last time, before the most recent time yesterday, that I did a water change, I happened to test the water about 48 hours after I had put in into the 25 L containers I use. I tend to fill the containers and let them get to room temperature for 24-48 hours. I put the API tap water condition in at the time I run the taps into the containers. I tested the water just randomly before the water change and it was coming up about 1.0ppm nitrite. I chucked the water and didn't do the water change. Thought a one off.

I then wondered if there is some kind of organic material in the water containers that is making the nitrite reading go from about 0.1 to about 1.0ppm in 48 hours, but this just can't be the case.

Same thing happened yesterday. After my tap water had been sitting for 48 hours since adding API conditioner, the nitrites were reading about 1.0ppm nitrite again. This is purple on the API test kit. I used the water and did a 50% water change in a tiny 25 L tank housing cichlid fry. I assumed a false-positive nitrite reading. This tank had undetectable nitrite prior to the water change, a very mature filter, and after the 50% water change was reading about 0.5ppm to 0.75ppm nitrite on the scale. After a few hours, the nitrite level in this tank dropped by about 50%, and about 6/7 hours after the water change, had returned to undetectable nitrite levels. All the fish were fine, no change in behaviour or colour.

If it's a false positive nitrite reading, how comes the action of the biological filter "removed" the nitrite slowly to zero, or, coincidentally, the API conditioner deactivated over that period, and therefore no more false positive result?

I then added a tiny bit of API water conditioner to both regular tap water and water I got from a tank of mine. Both times, when I did the nitrite reading it went from 0.0 to about 0.1ppm after adding the conditioner (so if you know the API test, from sky blue to slightly darker blue). So adding some API condition to the test water (just a drop or two) changes the nitrite reading, but didn't change it from blue to purple.

So, I am figuring the longer the API conditioner is in the water, the more of a false positive for nitrite?

I looked on Googe for a while and there was nothing about this. The only hits than come back are Seachem Prime causing false positive ammonia readings.

 

[Essjay]

I have used API Tap Water Conditioner for years and never seen a reading other than zero for nitrite (except during a fishless cycle when it is expected). Not even when I forgot to turn the filter back on after it had slipped and I straightened and only realised at the next water change.

And other members who use this water conditioner have never mentioned this either.

 

[AJ356]

I have used API Tap Water Conditioner for years and never seen a reading other than zero for nitrite (except during a fishless cycle when it is expected). Not even when I forgot to turn the filter back on after it had slipped and I straightened and only realised at the next water change.

And other members who use this water conditioner have never mentioned this either.

Yes, and nothing on Google. Zero. Strange. I am more curious than worried.

 

[MaloK]

Could it be the opposite ?

Your water really contains nitrite but the API tap water conditioner inhibits the results instead. When the effects of the conditioner diminish the real level shows up. Then your bio-filtration removes it in the tank ?

Have you tried to test the water before you add the conditioner ?

 

[AJ356]

Could it be the opposite ?

Your water really contains nitrite but the API tap water conditioner inhibits the results instead. When the effects of the conditioner diminish the real level shows up. Then your bio-filtration removes it in the tank ?

Have you tried to test the water before you add the conditioner ?

Good idea, but my tests on untreated tap water are 90% 0.1ppm to 0.25ppm nitrite and that's 100 odd tests over the years with various kits etc (normal test kits). I think i got over 0.25ppm a couple of times, but never over 0.50ppm. Usually, I'd say my tap water averages about 0.1 to 0.15ppm nitrite, rarely undetectable levels.

Nitrate on the other hand is normally about 20ppm from the tap. Essjay would have to leave her tanks without a water change for 1 year before they have my nitrate tap levels

 

[MaloK]

Something you can do, Test a sample of water for nitrate and take note of the results, Add a good 5 ppm of chlorine in the water mix it and let it stand until the chlorine evaporates, it will oxidize all nitrite to nitrate then re-do the nitrate test. If they raised in between.

I would think your municipality is using chlorine to oxidize nitrite, that would concur with your constant nitrate level in your tap.

 

[MaloK]

My next tough would be that the water conditioner when neutralizing chlorine force the release of Nitrite bounded but not already oxidized.

Would have to study the oxidation speed of nitrite... But I tend to think that oxygen level has the major influence in the process.

 

[Essjay]

Out of curiosity, what does your water company's water quality report give for both nitrite and nitrate?

The official upper limits are
nitrate - 50 ppm ("Occurs naturally from both mineral or soil processes and from agricultural activity")
nitrite - 0.5 ppm ("May be associated with the presence of ammonia or nitrate in river water")

 

[AJ356]

My next tough would be that the water conditioner when neutralizing chlorine force the release of Nitrite bounded but not already oxidized.

Would have to study the oxidation speed of nitrite... But I tend to think that oxygen level has the major influence in the process.

Thank you.

I am also going to see if the nitrite readings of the tapwater once adding the conditioner are dose dependent on the amount of conditioner used.

Something that I forgot to mention earlier, is that I think I am probably a bit too liberal (overdosing) with the conditioner, as it's potent.

The instructions are 5ml conditioner per 114 litres of tap water to detox chloramines, and I use 25 litre tubs that I only fill to about 15 litres to make it easier on my back. So I am dosing conditioner for 15 litres. Doing the maths, I'd only need to use about 0.7ml of conditioner for 15 litres. I bet I use more, comfortably more.

 

[AJ356]

Out of curiosity, what does your water company's water quality report give for both nitrite and nitrate?

The official upper limits are
nitrate - 50 ppm ("Occurs naturally from both mineral or soil processes and from agricultural activity")
nitrite - 0.5 ppm ("May be associated with the presence of ammonia or nitrate in river water")

I looked at this a few years ago, will dig up the latest one and post back soon

 

[AJ356]

Out of curiosity, what does your water company's water quality report give for both nitrite and nitrate?

The official upper limits are
nitrate - 50 ppm ("Occurs naturally from both mineral or soil processes and from agricultural activity")
nitrite - 0.5 ppm ("May be associated with the presence of ammonia or nitrate in river water")

All mg/l

Nitrate min 24.0, mean 28.3, max 34.5
Nitrite min 0.021, mean 0.126, max 0.317

Those nitrite readings are more or less exactly what I see from my tap water nitrite test kit readings over the years and in the same kind of percentage

I've always really rated the API nitrite test kit, apart from if over 0.50 the colour chart is hard to read

 

[AJ356]

I have used API Tap Water Conditioner for years and never seen a reading other than zero for nitrite (except during a fishless cycle when it is expected). Not even when I forgot to turn the filter back on after it had slipped and I straightened and only realised at the next water change.

And other members who use this water conditioner have never mentioned this either.

With this, I was wondering how many people would actually think to test their tank after a water change if they weren't looking for a problem? I mean, I bet most people would only test their tank immediately after a water change to compare the results if before the wayer change there was an issue with ammonia, nitrite, nitrate or pH.

 

[MaloK]

Thank you.

I am also going to see if the nitrite readings of the tapwater once adding the conditioner are dose dependent on the amount of conditioner used.

Something that I forgot to mention earlier, is that I think I am probably a bit too liberal (overdosing) with the conditioner, as it's potent.

The instructions are 5ml conditioner per 114 litres of tap water to detox chloramines, and I use 25 litre tubs that I only fill to about 15 litres to make it easier on my back. So I am dosing conditioner for 15 litres. Doing the maths, I'd only need to use about 0.7ml of conditioner for 15 litres. I bet I use more, comfortably more.

That can also be tested easily, Take a tube of 5 ml for a test, put 2 drops of APi in it and perform a normal test.

You should have a really exaggerated results if there's some kind of interaction between the products.

 

[Essjay]

So your water company's testing lab says you have nitrite in your tap water. I did read in the Drinking Water Inspectorate reports from 2014 or 15 that nitrite occurs when chloramine is used. Unfortunately they don't have reports from that long ago on their website now.


I bought a small bottle of API Tap Water Conditioner with a dropper in the lid and when it was all used I refill from bigger bottles. The dose rate is 1 drop per US gallon/3.8 litres. I make up 8 litres in a 10 litre bucket using 2 drops conditioner. Your 15 litres would need 4 drops.
However I did discover that at one time, the larger bottles had a different dose rate from the smaller bottles so the amount of water treated by 1 drop varied according to bottle size.
I put the drops in the bucket then turn the tap on full to mix it all together as much as possible. (I also took the tap insert apart and removed part of it to make the flow faster)




Edit - found it! I'd forgotten I'd saved the pdf of the DWI 2014 Northern England report.

"Nitrite may be formed when chloramine is used as the residual disinfectant to maintain the microbiological quality in the distribution network. The formation of nitrite is controlled by careful optimisation of the chloramination process (list of places using chloramine)
Nitrite can also form in samples of water, after collection and before analysis, especially if the sample is not kept cool."

 

[MaloK]

I always completely remove the aerator from the taps used to maintain aquariums.