How long is water "good" for to test Nitrates/Alkalinity/Phosphate w/ Hannah Checkers?

[danR777]

I looked for a previous question for this but could not find (maybe because it is common sense lol ):

If I collect water yesterday for example, and test it the next day.. there really is no difference in parameters for the normal attributes?

Is there some sort of shelf life for accuracy?

 

[Rmckoy]

I looked for a previous question for this but could not find (maybe because it is common sense lol ):

If I collect water yesterday for example, and test it the next day.. there really is no difference in parameters for the normal attributes?

Is there some sort of shelf life for accuracy?

If you collect water from your tank now why would you leave it till tomorrow to test ?

that’s only going to tell you what the test result was from yesterday …

why ? Is my only question.

 

[Joe31415]

There's an easy way to find out. Pull some a few cups of water from the tank today, use some of it to test and leave the rest. Then test it again the next day/week etc.
It wouldn't surprise me if microscopic algae could consume some of the nutrients (or die and release them), but then it also wouldn't surprise me if that wasn't enough to make a measurable difference.

Also, I have to assume you don't have your own test kits and you're taking it somewhere else to be tested, hence it being out of the tank overnight. Because otherwise I can't think of a single good reason not to toss it and get a fresh sample.
Remember, even if the sample is good, it's going to reflect the numbers at the time it was removed from the tank and those numbers could very well be entirely obsolete a day later.

 

[gbru316]

Test it as close as possible to when the sample was taken.

The longer you wait, the more time there is for it to deviate from the main tank parameters due to evaporation, biological processes, or something else.

 

[danR777]

Thanks guys for replying so quick:...

Usually I collect the water pre-water change and then will compare it a day or two later post water change..

I'd rather not have to test and then test again... I like to do all the tests in one shot basically if that makes sense, that really is all... obviously the current water is what matters of course... I usually like to gauge improvement by % of water change done manually or through my AWC's....

 

[gbru316]

Thanks guys for replying so quick:...

Usually I collect the water pre-water change and then will compare it a day or two later post water change..

I'd rather not have to test and then test again... I like to do all the tests in one shot basically if that makes sense, that really is all... obviously the current water is what matters of course... I usually like to gauge improvement by % of water change done manually or through my AWC's....

No need to measure improvement. It's easily calculated if you know the parameters of your make-up water. For instance, using RO/DI nitrate should be 0.


If you test your tank and you've got 10 ppm nitrate, and do a 10% water change, you now have 9 ppm nitrate (10% of 10 is 1, so subtract the 1 ppm you removed from the measurement). And at these numbers, the difference may very well be within the tolerance of the test set so it's a moot point, really. Longer term trends are what matter most.

 

[danR777]

No need to measure improvement. It's easily calculated if you know the parameters of your make-up water. For instance, using RO/DI nitrate should be 0.


If you test your tank and you've got 10 ppm nitrate, and do a 10% water change, you now have 9 ppm nitrate (10% of 10 is 1, so subtract the 1 ppm you removed from the measurement). And at these numbers, the difference may very well be within the tolerance of the test set so it's a moot point, really. Longer term trends are what matter most.

I never really see that with Phosphates... Nitrates seem to be linear like that, but phosphates never do for me... its always some sort of variance to them

 

[gbru316]

I never really see that with Phosphates... Nitrates seem to be linear like that, but phosphates never do for me... its always some sort of variance to them

Because it's a small value. The accuracy of the checker (Phosphorous ULR) is +/- 0.015 ppm.

If your Po4 is 0.1 ppm and you do a 10% change, you're only changing in-tank Po4 by 0.01 ppm. But repeating that test could yield a swing of 0.03 ppm just because of the accuracy of the checker. It's literally impossible to detect a change of 0.01 ppm reliably because you're always going to have that tolerance included in the measurement.


This is why I mentioned long term trends being more important than single point tests. Over time, that +/- 0.015 ppm tolerance gets "lost in the noise."

 

[Dburr1014]

I never really see that with Phosphates... Nitrates seem to be linear like that, but phosphates never do for me... its always some sort of variance to them

This is because phosphates are bound in rock/sand. When the water column is lowered in po4 the rock leach it out to balance.

 

[danR777]

Thank you all

The binding and then leaching out is interesting to me: Wonder what force comes into play for it to "balance" itself, like what drives that? homeostasis?

 

[Dburr1014]

Thank you all

The binding and then leaching out is interesting to me: Wonder what force comes into play for it to "balance" itself, like what drives that? homeostasis?

Actually, that sounds about right.
But, I'm no scientist.

 

[Malcontent]

Yeah, it does matter for some measurements. Ammonia, for example, has to be refrigerated and the pH lowered to 2 then raised again for test. Too much trouble if you ask me and at most I would try to get away with refrigeration only for a few hours.

https://www.eurofinsus.com/media/447768/appendix-d-section-5-attachment-holdtime-container-list_2016-july.pdf

Interesting that there's no acceptable method to preserve samples for chlorine testing and samples are to be tested on site. That means an automated tester has to be in place or someone has to drive out there with a portable tester.

 

[danR777]

Yeah, it does matter for some measurements. Ammonia, for example, has to be refrigerated and the pH lowered to 2 then raised again for test. Too much trouble if you ask me and at most I would try to get away with refrigeration only for a few hours.

https://www.eurofinsus.com/media/447768/appendix-d-section-5-attachment-holdtime-container-list_2016-july.pdf

Interesting that there's no acceptable method to preserve samples for chlorine testing and samples are to be tested on site. That means an automated tester has to be in place or someone has to drive out there with a portable tester.

Oh cool... that is interesting ... I just read some ICP testing sites are doing Nitrate / Phos tests now...so if it survives in the USPS for a few days..... but i;m sure its way better than a Hannah Checker

 

[Malcontent]

Oh cool... that is interesting ... I just read some ICP testing sites are doing Nitrate / Phos tests now...so if it survives in the USPS for a few days..... but i;m sure its way better than a Hannah Checker

I think ICP just quantifies the atoms and not the molecular forms so it can't distinguish between ammonia, nitrite, or nitrate. So even if the sample degrades and ammonia becomes nitrate it'll still give the same nitrogen content which isn't useful if you're trying to measure ammonia...