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Discussion Starter · #61 ·
You can't mix a known sample of nitrate in water, for example, then add the test reagent to get the color, then save that colored sample to refer back to later. The color comes from dyes in the reagents, and dyes are not stable chemicals. You might be able to store them for a week or so, but definitely not for years.
 

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Any way to calibrate a GH test? My API tests are impossible to read. The color gets just slightly darker green/green yellow with each drop but does not ever make the dramatic change that I have seen of other peoples tests. I guess it may have been a bad kit.
 

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Discussion Starter · #64 ·
My experience is that GH test kits have a very limited shelf life before they just stop changing color when you try to use them. There is no reason I'm aware of to measure GH with much accuracy, so even a poor test kit, that is off 20% on the readings, is adequate. For that reason I don't think it is worth the trouble to figure out a good easy way to calibrate a GH test kit, but I'm sure it can be done.
 

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My experience is that GH test kits have a very limited shelf life before they just stop changing color when you try to use them. There is no reason I'm aware of to measure GH with much accuracy, so even a poor test kit, that is off 20% on the readings, is adequate. For that reason I don't think it is worth the trouble to figure out a good easy way to calibrate a GH test kit, but I'm sure it can be done.
Agree - I have an 10 year-old API GH test kit and it does the same thing - it never shows the definite color change. You could ask around locally to see what the tap GH is - maybe LFS has a test kit and could run a test for you as well.
 

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You can skip GH and buy a cheap digital TDS meter ($10). TDS is a good way to test water softness/hardness.

You can make a simple NaCl (table salt) calibration solution. 1mg/L is 1ppm. And there's about 5690 mg in a teaspoon. A meter only goes up to 1000ppm so you'll have to dilute the solution.
 

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A question on behalf of us AquaDummies:
KNO3 = SaltPeter? Or where would one find this?

I have two API test kits whose nitrate tests report very different results on the same sample. One, less than a year old, reports upward to 160 ppm while the other reports 20ppm.
 

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A question on behalf of us AquaDummies:
KNO3 = SaltPeter? Or where would one find this?

I have two API test kits whose nitrate tests report very different results on the same sample. One, less than a year old, reports upward to 160 ppm while the other reports 20ppm.
first:
https://www.walmart.com/ip/Potassium-Nitrate-Powder-KNO3-1-2-Lb/730344998


Could give you the standard answer that the second reagent really isn't a solution but a suspension. If not properly beat to bejesus it will be inaccurate..
One possibility is it was accidentally used up prev in big cloudy clumps..


.

Switched to Seifert personally..
 

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first:
https://www.walmart.com/ip/Potassium-Nitrate-Powder-KNO3-1-2-Lb/730344998


Could give you the standard answer that the second reagent really isn't a solution but a suspension. If not properly beat to bejesus it will be inaccurate..
One possibility is it was accidentally used up prev in big cloudy clumps..


.

Switched to Seifert personally..

Yeah, I followed protocol and 'shook vigorously' for a full 30 seconds, always do. Maybe I'll try beating it too.
One other thing I noticed was the two vials side-by-side didn't have exactly the same amount of liquids. I actually redid the test thinking I miscounted the number of drops but the one showing lower ppm had, at most, 1/16" less liquid. Samples are equal poured till the bottom of the miniscus reaches the line.
 

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Switched to Seifert personally..
+1.

I use reference solutions to do a side by side test with Salifert and API test kits and posted it in my journal.

https://www.plantedtank.net/forums/12-tank-journals/1020497-greggz-120g-rainbow-fish-tank-camera-pro-mode-settings-8-12-2018-a-56.html.

Even a new API test was not very accurate. And like mentioned, if you don't pound the heck out of it EVERY time, then it's worse.

The Salifert kit was spot on.

So just saying I would take whatever reading you get with the API as a VERY rough estimate, and wouldn't base too many decisions around it.
 

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I think what happens and what Jeff was hinting at is that the chemicals in one test bottle may no longer be what they should. When new and we fail to shake them well enough, which is a pretty common thing apparently, we get too much of one component used out of that bottle and each time we do a test, we use more of that portion until there is no way we will get the correct answer even when beating it to death. My thinking, for simple, is that the one bottle is more than one item until we mix them well. So if we use that bottle, we get too much used of one of those items and then when we get into shaking it really well, we have missed the prime /correct mix in that bottle.
For example, if we added salt to water and did not mix it well to dissolve the salt, we might turn the bottle over, use the salt out and not really ever get the true salt water mix we wanted? So then we try really, really, mixing but much of the salt is already gone from the prior uses?
Shake them well? I even made a shaker for a reciprocating saw and never got the good answers! I gave up on a test that was that difficult to use and also went to the Salifert brand test kit to get good results. I can see the pink much better and I am willing to pay the extra to get a usable/reliable answer versus a cheap but unreliable test report.
 

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I think what happens and what Jeff was hinting at is that the chemicals in one test bottle may no longer be what they should. When new and we fail to shake them well enough, which is a pretty common thing apparently, we get too much of one component used out of that bottle and each time we do a test, we use more of that portion until there is no way we will get the correct answer even when beating it to death. My thinking, for simple, is that the one bottle is more than one item until we mix them well. So if we use that bottle, we get too much used of one of those items and then when we get into shaking it really well, we have missed the prime /correct mix in that bottle.
For example, if we added salt to water and did not mix it well to dissolve the salt, we might turn the bottle over, use the salt out and not really ever get the true salt water mix we wanted? So then we try really, really, mixing but much of the salt is already gone from the prior uses?
Shake them well? I even made a shaker for a reciprocating saw and never got the good answers! I gave up on a test that was that difficult to use and also went to the Salifert brand test kit to get good results. I can see the pink much better and I am willing to pay the extra to get a usable/reliable answer versus a cheap but unreliable test report.

Yep, I get all that and everything else posted. Thanks!
I have both a pound of KNO3 and a Salifert test on order now.


I'm kind of returning to the hobby, and for the first time have become concerned about water testing. Never seemed to be an issue in previous planted tanks; water was always clear, fish happy, plants grew. But now in Aquarium Hobby v.2.0 I'm experimenting with anoxic filtration using Safe T Sorb as a substrate and plenums in a 65 gallon and a Fluval Edge 6 gal. (it was a freebie) so these metrics are more critical. 4 months into it I'm finding (according to API): pH 7.6-7.8, Ammonia 25 -50 ppm, Nitrates 0 and Nitrates 80 - 160. Fish seem happy, plants look healthy (who wants some Hornwort?). Algae was a bit of a problem in the Edge but breaking up the lighting period into two parts with a 2 hour break seemed to being that into check. No CO2 being added.


But before I do anything else I need to know what's happening with the water.
Thanks for the valuable feedback. Wish I'd known about the API issues 4 months ago!
 

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Calibrating Test Kits - for non-Chemists
API NO3 Test Kit

Thought I’d post my results for the heck of it ☺
  • All testing as per API NO3 Test Kit Instructions.
  • API Test Bottle #2 shaken for 1 min before each test.
  • All photos on the LHS are taken with the test vial flat against the card.
  • All photos on the RHS are taken spaced off the card by my index finger (approx 1/2”)
  • Lighting: Chihiros A II Series A451 @50% Intensity (1950lm 21w 8500K)
  • Camera: iPhone XR (No filters or aperture adjustment)
API NO3 Calibration Test for 800 ppm nitrate standard water.
  • TDS: 670ppm
  • Reading API NO3 Card @ Test Station: N/A - No test taken
Test 1.
API NO3 Calibration Test for 100 ppm nitrate standard water.
  • TDS: 90ppm
  • Reading API NO3 Card @ Test Station: 80ppm
    Product Rectangle Fluid Font Material property
Test 2.
API NO3 Calibration Test for 50 ppm nitrate standard water.
  • TDS: 45ppm
  • Reading API NO3 Card @ Test Station: 40ppm
    Liquid Rectangle Fluid Solution Highball glass
Test 3.
API NO3 Calibration Test for 25 ppm nitrate standard water.
  • TDS: 23ppm
  • Reading API NO3 Card @ Test Station: 30ppm
    Liquid Fluid Rectangle Orange Font
Test 4.
API NO3 Calibration Test for 10 ppm nitrate standard water.
  • TDS: 9ppm
  • Reading API NO3 Card @ Test Station: 10ppm
    Liquid Rectangle Fluid Amber Drinkware
Test 5.
API NO3 Calibration Test for 5 ppm nitrate standard water.
  • TDS: 2ppm
  • Reading API NO3 Card @ Test Station: 0-5ppm
    Liquid Tableware Solution Drinkware Product
Test 6.
API NO3 Calibration Test for Distilled Water:
  • TDS: 0ppm
  • Reading API NO3 Card @ Test Station: 0ppm
    Rectangle Fluid Font Material property Gas
 

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