View Full Version : Nitrite Testing Question

01-27-2017, 10:38 AM

I'm been a lurker on this site for quite a while and have learned an enormous amount by doing so. I want to thank all of you who are so generous with sharing your knowledge with people like me, who knew almost nothing before finding this site.

I had an odd experience yesterday and I would like your opinions.

I brought in some water from my pond, which had a water temperature of just over 50 degrees at the time. I did my usual tests, and the nitrite level was a little less than .25, but definitely over 0. I wasn't very happy with that, and a few hours later, I tested the same water sample again. This time I got a reading of 0. For good measure, I tested it a 3rd time and got the same result of 0.

I have found some information that says that the water should warm to room temperature before testing, but I've never done that before. Besides, my fish are living in the cooler water, and it would seem to me that I should be testing the water they actually live in.

My question is, can warming the water cause a different result in the test? And how does this relate to my fish? It's very possible that I just made a mistake and perhaps added too many drops. But this has gotten my curiosity up.

Thanks for your help.

01-27-2017, 12:43 PM
You mean you brought a batch of water, acclimated it, tested +. Retested the same batch now it's - .Or did you go out and got a new batch (not acclimated) and that tested - (neg)?

01-27-2017, 12:56 PM
I brought in a sample of water from the pond, testing it right away. It was still at pond temperature, or close to that, around 50 degrees. I got a reading of close to .25 nitrite.

I let that same sample of water sit and tested it again, a few hours later. I assume that by then it had heated to room temperature. At that time, the water tested at 0, both times that I tested.

I hope that answers your question.

01-27-2017, 12:59 PM
Just to clarify the situation, it seems that the exact same water sample went from + to -, simply by warming the water.

01-27-2017, 02:15 PM
What happens is that the chemical reaction that leads to the color change when you do the testing is affected by temperature. When the directions state that you should read at 10 minutes, when the water is cold, it takes longer. the nitrite concentration did not change. What changed was the ability of the test to read the nitrite concentration.

01-27-2017, 02:26 PM
Thank you for that explanation.

Why would the nitrite level read higher when the water is cold? It seems it would be just the opposite.

There is nothing I can find in the instructions to indicate that the sample water should warm to room temperature. I have been testing it immediately. I guess I'll have to change my methods.

01-27-2017, 03:35 PM
Just to clarify the situation, it seems that the exact same water sample went from + to -, simply by warming the water.

I know what you mean. It's weird. Test your pond water again (fresh from pond) and see if you can replicate. Dont try anything new. Also check if there is an expiry date on the bottle.

Its funny how you didnt throw away the first batch of water when typically most people would :)

01-27-2017, 03:37 PM
It depends on which test you are using and on the direction of the color change. My experience with the API kit is that it takes about 20 to 30 minutes to get to the final color change when the water is less than about 65 degrees. Most manufacturers have never tested their products at different temperatures. I suspect that for almost all of the test kits we buy, the directions assume the water will be at room temperature (68 to 77 deg F). I agree that it would be best if the directions so indicated.

01-27-2017, 04:05 PM
Thanks for all the help. I do appreciate it.

I'm using the API liquid drops. This is a fairly new test kit, so I'm wondering if I just messed up when I added the drops.

I do tend to leave the tests and sample water sitting around for a while. I just get busy with something else and forget about them. I'm not one to sit around and watch for the results.

I just did a new test on cold water from the pond today, and it's reading 0 nitrites after 20 minutes or so. I'm starting to think I just messed it up before. I'll check it again when the water sample warms up, but I don't expect a different answer now.

Thanks again for all the information. And thanks Rick, for clarifying what "room temperature" is. I was wondering about that, too.

I'm always glad to learn something new, so this has been a very positive thread for me.

01-27-2017, 05:02 PM
I use API tests for all water parameters, are there better test kits?

01-27-2017, 05:12 PM
API is what I use, but there are others.

01-27-2017, 08:42 PM
API is good, but there are more expensive that read finer, using equipment, rather than eyeball color changes. In the old days before heating my ponds, I would take the tube of water, pre drops and run it back and forth between my hands to raise the temperature to close to room temperature. When you are relying on chemical changes to do the indicating, the change is both temperature and time dependent. The general rule for chemical reactions is that if the temperature drops 10*C, (18*F) the time for the reaction doubles and vice versa, if the temperature goes up 10*C the time is cut in half. The instructions don't get into the temperature dependence, as it would complicate the instructions. Most people using the kits are testing aquarium water in a house, much of it heated.