Dosing KNO3 but Nitrate test kit reads 0 ppm - The Planted Tank Forum
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post #1 of 8 (permalink) Old 04-17-2015, 09:50 PM Thread Starter
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Dosing KNO3 but Nitrate test kit reads 0 ppm

Recently my root tabs were depleted so I switched to dry dosing and my plant growth/health has improved in just a few days and algae growth has slowed.

KNO3 is the largest component of my dosing. I did a nitrate test about 12-16 hours after adding the second KNO3 dose and the test said I had 0 ppm nitrates! Does KNO3 not register on the API nitrate test or does this mean that my plants had already consumed all of the nitrate I added? Should I be dosing more KNO3?

This is in a 10 gallon mid-tech tank (reduced EI dosing).
Lighting: Marineland double-bright LED (25-30 PAR at substrate, 7 hours per day)
Substrate: Eco-complete
  • KNO3 (1/8 tsp 2x per week)
  • KH2PO4 (1/32 tsp 1x per week, my tap water already has some phosphorus)
  • Flourish Comprehensive (1.5 ml 2x per week)
  • Flourish Excel (1.5 ml daily)

I dose by taking out a cup of tank water, dissolving the ferts into it and pouring it back into the tank. I am dosing micros on different days than macros
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post #2 of 8 (permalink) Old 04-17-2015, 10:17 PM
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Did you shake bottle #2 of the nitrate test vigorously?
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post #3 of 8 (permalink) Old 04-17-2015, 10:18 PM Thread Starter
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Nope, didn't shake it. I'll try that when I get home.
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post #4 of 8 (permalink) Old 04-17-2015, 10:32 PM
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Don't just shake it - shake it until your wrist aches.... Pay attention to the instructions for this test or you will get a zero result, even on 1000ppm stock solutions...
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post #5 of 8 (permalink) Old 04-17-2015, 10:34 PM
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You need to thousand one, one thousand two...and get to about 30.
I use 40. I shake the first bottle 10 seconds and the second bottle 40 seconds.
I have two 10g tanks. I dose that amount once a week. But I split it half and half/w K2SO4
and I get about 30 for my reading. Orange just before turning to red.
At times I use 1/32 KNO3 and 1/32+1/16 K2SO4 to bring down the nitrates.
I do the test just before the water change.

The shortest distance between any two points is a straight the opposite direction...
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post #6 of 8 (permalink) Old 04-18-2015, 03:01 AM Thread Starter
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Ok, not shaking the nitrate tests was definitely the problem. My test tube was nearly red. I'm doing a good sized water change and will definitely be lowering my dosage.

Thanks for the help, probably saved my fish!
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post #7 of 8 (permalink) Old 04-18-2015, 08:04 AM
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teat kits

Calibrating your test kit would be a good idea. And closely follow the instructions.

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post #8 of 8 (permalink) Old 04-18-2015, 01:38 PM
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The second bottle has little particles of Zinc in it that settle to the bottom. You really have to shake it to get those particles back into the solution.

The problem is that if you dont shake it enough, eventually the concentration of zinc particles increases in the bottle and the test starts to give really high results.

I always replace the test kit when it gets about 1/2 empty and the old test kit always reads higher, sometimes by twice as much, as the new test kit.

So be diligent with the shaking. I also wack the bottle a few times on something hard to help mix up the particles.
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estimative index, excel and ferts, kno3, nitrate

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