Strange nitrate test. Opinions?

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iktomiwicasa

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Aug 26, 2006
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Strange nitrate test. Opinions? Pics

I have been cycling (fishless) up my 80 gallon tank, and testing water parameters using AP tests. When checking for nitrates, when I add the FIRST reagent to the test sample, it turns quite dark, much much darker than is normal for my other tanks. It makes it hard for me to trust the reading for this tank. The only things different with this tank is a large piece of driftwood and a sand/flourite substrate. Same source water. Could my wood and/or the substrate be causing some sort of reaction with the first reagent in the nitrate test? Kinda scratching my head on this one :confused: ....the test behaves normally in my other two tanks. I've inserted a carbon packet into the filstar xp3 to remove any potential reactive chemicals in the tank, and I'll check again tomorrow. Has anyone else had a similar experience?
 
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This image shows test tubes from two different tanks after adding the FIRST AP nitrate test reagent. The tube on the left is from my 80 gallon tank, and as you can see is much darker than normal. The tube on the right is from a 20 gallon tank, and shows a more normal color after adding the first reagent.

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The driftwood in the 80 gallon.

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nice chunk of driftwood.

I'm more curious how the test behaves after you add the second reagent and the final results.
 
Fill one of the tubes up with the 80 gallon water and hold it up to a white piece of paper. Is the water brownish? I suspect you are seeing tannins from the driftwood discoloring the water enough to make the first reagent color look abnormal.
 
webcricket said:
Fill one of the tubes up with the 80 gallon water and hold it up to a white piece of paper. Is the water brownish? I suspect you are seeing tannins from the driftwood discoloring the water enough to make the first reagent color look abnormal.
Click to expand...

I thought of that. The wood has tinted the water ever so slightly, but you can only detect it in a large volume. You can't see it in the test tube, and it would have to be quite heavily tinted to account for the color difference.
 
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