Trouble reading nitrates test - The Planted Tank Forum
 
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post #1 of 5 (permalink) Old 10-15-2015, 09:46 PM Thread Starter
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Trouble reading nitrates test

Hello. I have a lot of trouble reading my nitrates liquid test (API master test kit). Anything past 10 is so hard for me to tell the difference between the different reds. When I tested my water last night, I honestly couldn't tell if it was 15 or 50. The only way I can really make out any difference is if I hold the test tube up against the card, and look at the colors through the tube and try to find one that blends in the most.

Does anyone have any suggestions on how to better read the test? Indoors? Outdoors? Thank you for any help.

I have no idea what I'm doing!
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post #2 of 5 (permalink) Old 10-15-2015, 10:13 PM
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I usually read it indoors, with a north facing window or glass door behind me. Hold the tube against the card, but between the different test colours so it is against the white. Aim for a position where there is no reflection or minimal reflection against the glass tube.

I find this is the best way to help differentiate the colours. I can at least get it down to two choices side by each, if not just one choice.

Oh, I can't do this during twilight hours. Pretty much mid-morning to mid-afternoon is the only time that works for me.

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post #3 of 5 (permalink) Old 10-15-2015, 10:23 PM
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If you have a decent monitor, take this test to see how much of the problem is your color perception.
Color Test - Online Color Challenge | X-Rite

I expect it is best to evaluate the colors in daylight. I've converted most of my house to http://smile.amazon.com/gp/product/B00KW1MMZ8/ref=od_aui_detailpages00?ie=UTF8&psc=1 and use that to evaluate the test colors. It isn't exactly daylight, but close and much better than the yellow of warm lighting.

That said, I can't get a precise reading either. However, I can narrow it down a bit more than 15-50. I can determine if it is zero, around 25, or higher than I like.

I hold the tube a little over the white between color charts and angle the whole thing to the light so I see a clear color all the way across the side of the tube. Then I try to look for how much red is in the color. It is difficult to match a translucent color with an opaque swatch, but try to think about how red it is compared to how red the swatch is.

With this test it is important to follow the instructions exactly. Shake bottle 2 for 30 sec. before adding drops. Some say bang the bottle against something to loosen settled material. After adding drops from bottle 2, shake the tube for a full minute. Then time for 5 min.
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post #4 of 5 (permalink) Old 10-15-2015, 10:25 PM
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Honestly, those tests are hard to read at best and inaccurate at worst. Many people make a calibration reference mix.

Here's my how I do mine:
  • Make a rough guess of where I expect the nitrates to be (this gets easier over time).
  • Fill a test tube to the line with the reference solution with a concentration just lower than the range I think (or hope) the tank water will be in.
  • Do the same for the reference solution just higher than I expect in another tube. Also put the tank sample water in a third tube.
  • Arrange the tubes in order with the low value reference, then the tank sample, then the high value reference. (I stand them on a white paper on a table or counter)
  • Add solution one to all three tubes.
  • Add solution two one drop at a time. Put the first drop in all three, then the second in all three and so on.
  • Quickly cap all three and holding them in the sorted order shake and set back down on the paper.
  • Let sit for a couple minutes. As the color develops it will develop at different rates based on the nitrate concentration. If the color of the tank sample develops quicker than the low reference solution but slower than the high reference solution then the tank nitrate level is in the range between the two. If the tank sample is faster or slower than both repeat with adjusted reference sample values.

So, if I think my tank should be at about 20 ppm nitrate I will test the tank water and the 10 ppm and 25 ppm reference samples. If it's higher than both I'll repeat the test with the 25 ppm and 50 ppm reference samples, or if it was lower than both I'll repeat with 5 ppm and 10 ppm samples. Otherwise I know I am somewhere between 10 and 25 ppm.

This is how I do it at least. It's possible the hardness of the tank water relative to the RO based reference samples may make a difference, but it seams to get me in the ballpark better than the reference card does, especially since the reference card says my tap water is over 20 ppm nitrate! It's certainly more time consuming though.
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post #5 of 5 (permalink) Old 10-15-2015, 10:55 PM Thread Starter
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Quote:
Originally Posted by Argus View Post
If you have a decent monitor, take this test to see how much of the problem is your color perception.
Color Test - Online Color Challenge | X-Rite
Good news! I'm not color blind!

Quote:
Originally Posted by iceburg View Post
Honestly, those tests are hard to read at best and inaccurate at worst. Many people make a calibration reference mix.

Here's my how I do mine:
  • Make a rough guess of where I expect the nitrates to be (this gets easier over time).
  • Fill a test tube to the line with the reference solution with a concentration just lower than the range I think (or hope) the tank water will be in.
  • Do the same for the reference solution just higher than I expect in another tube. Also put the tank sample water in a third tube.
  • Arrange the tubes in order with the low value reference, then the tank sample, then the high value reference. (I stand them on a white paper on a table or counter)
  • Add solution one to all three tubes.
  • Add solution two one drop at a time. Put the first drop in all three, then the second in all three and so on.
  • Quickly cap all three and holding them in the sorted order shake and set back down on the paper.
  • Let sit for a couple minutes. As the color develops it will develop at different rates based on the nitrate concentration. If the color of the tank sample develops quicker than the low reference solution but slower than the high reference solution then the tank nitrate level is in the range between the two. If the tank sample is faster or slower than both repeat with adjusted reference sample values.

So, if I think my tank should be at about 20 ppm nitrate I will test the tank water and the 10 ppm and 25 ppm reference samples. If it's higher than both I'll repeat the test with the 25 ppm and 50 ppm reference samples, or if it was lower than both I'll repeat with 5 ppm and 10 ppm samples. Otherwise I know I am somewhere between 10 and 25 ppm.

This is how I do it at least. It's possible the hardness of the tank water relative to the RO based reference samples may make a difference, but it seams to get me in the ballpark better than the reference card does, especially since the reference card says my tap water is over 20 ppm nitrate! It's certainly more time consuming though.
Wow, this is intense! I'll see if I can do this myself. Thanks for all the help!

I have no idea what I'm doing!
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