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Discussion Starter · #1 ·
Hi, i just made my own nitrate fert using KNO3. Using rotalabutterfly, I measured 17.12 grams of the powder into a 350ml container. Each 5ml dose will give me 5ppm. However when i tested that solution for nitrates, Im getting a reading of 0. Does anybody know why?
 

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Your post indicates that you are measuring your concentrate solution and not the aquarium. Is this correct? If so, adding 17+ grams of KNO3 to 350ml of water is going to have an NO3 level off the chart, which should cause your test (if the test kits are the typical cadmium-reduction used in our hobby) to turn deep red.

If you are measuring your tank, after dosing 5ml, then your tank would have to be an 8-gallon tank in order to get a 5ppm NO3 reading, based upon the input numbers you provided.

The answer to your question is; yes, an NO3 test kit will measure the NO3 you dose. I suspect there is something wrong in the way you are using the calculator. Let us know what your tank size is, as that is probably where the miscalculation exists …if your tank is not 8 gallons.
 

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Discussion Starter · #3 ·
If so, adding 17+ grams of KNO3 to 350ml of water is going to have an NO3 level off the chart, which should cause your test (if the test kits are the typical cadmium-reduction used in our hobby) to turn deep red.
Yes im measuring directly from the concentrated solution. Im using a test strip that can read up to 500ppm but right now it doesnt even pick up 0ppm.
My calculations are all from rotalabutterfly. My aquarium is abt 30 litres. Dose to reach 5ppm is 5ml from a 350ml container so KNO3 needed is 17.12g.
 

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Then I would look to the test strip, which are notoriously unreliable, which may simply not measure beyond a certain point, but i'm not sure what their limitations are. It will probably give a reading that fits better if you measure your tank with it. Your numbers are all correct, based upon your tank size.

Most of us, in the planted tank world, use reagent-type tests, which are far more precise and reliable than test strips. I would recommend the Salifert NO3 ("Profi" kit, not the freshwater kit). If you are serious about plants, you will want to measure NO3 somewhat frequently and reliably.
 
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Yes im measuring directly from the concentrated solution. Im using a test strip that can read up to 500ppm but right now it doesnt even pick up 0ppm.
My calculations are all from rotalabutterfly. My aquarium is abt 30 litres. Dose to reach 5ppm is 5ml from a 350ml container so KNO3 needed is 17.12g.
If you add 17 grams to 350 ml of water, the NO3 ppm is above 30,000. This is well beyond the test strip's capability.

Someone correct me if my math is wrong, but that is likely why the test strips aren't working for you when measuring the concentrated solution.

Dose to reach 5ppm is 5ml from a 350ml container so KNO3 needed is 17.12g.
I doubled checked this math for you. It is correct. 17.12g of KNO3 in a 350ml solution will increase your 8 gallon tank by 5ppm of NO3 for every 5ml added.
 

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It does not have an odor, to me.

KNO3 has a molecular weight of 101.180 and K has a molecular weight of 39.0983:

39.0983 / 101.183 = 38.64% potassium
62.0817 / 101.180 = 61.36% nitrate
Can't comment on the test strips but KNO3 in solution should show up in reagent tests..

Make a reference solution and test..
I'm copying this in it's entirety since I found this is archived.
Those that are interested should c/paste for their own use.
How to Make Reference NO3 Solutions
Here's a way to make 10, 20, 30 and 40 ppm NO3 reference solutions:
  • Add 1.631 g of KNO3 to 1 L distilled or DI water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)
  • Add 2 mL of the 1000 ppm solution to 18 mL of distilled or DI water. This makes 20 mL of a 100 ppm NO3 solution.
  • Add 15 mL of the 100 ppm solution to 15 mL of distilled or DI water. This makes 30 mL of a 50 ppm NO3 solution.
To make a 10 ppm NO3 solution:
  • Add 2 mL of the 50 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 10 ppm NO3 solution.
To make a 20 ppm NO3 solution:
  • Add 4 mL of the 50 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 20 ppm NO3 solution.
To make a 30 ppm NO3 solution:
  • Add 6 mL of the 50 ppm solution to 4 mL of distilled or DI water. This makes 10 mL of a 30 ppm NO3 solution.
To make a 40 ppm NO3 solution:
  • Add 8 mL of the 50 ppm solution to 2 mL of distilled or DI water. This makes 10 mL of a 40 ppm NO3 solution.
How to Make Reference PO4 Solutions
Here's a way to make 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:
  • Add 1.433 g of KH2PO4 to 1 L distilled or DI water. This makes a 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution.)
To make 10 mL of a 100 ppm PO4 solution:
  • Add 1 mL of the 1000 ppm solution to 9 mL of distilled or DI water.
To make 20 mL of a 10 ppm PO4 solution:
  • Add 2 mL of the 100 ppm solution to 18 mL of distilled or DI water.
To make a 1.0 ppm PO4 solution:
  • Add 1 mL of the 10 ppm solution to 9 mL of distilled or DI water. This makes 10 mL of a 1.0 ppm PO4 solution.
To make a 2.0 ppm PO4 solution:
  • Add 2 mL of the 10 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 2.0 ppm PO4 solution.
To make a 3.0 ppm PO4 solution:
  • Add 3 mL of the 10 ppm solution to 7 mL of distilled or DI water. This makes 10 mL of a 3.0 ppm PO4 solution.
To make a 4.0 ppm PO4 solution:
  • Add 4 mL of the 10 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 4.0 ppm PO4 solution.
To make a 5.0 ppm PO4 solution:
  • Add 5 mL of the 10 ppm solution to 5 mL of distilled or DI water. This makes 10 mL of a 5.0 ppm PO4 solution.
 

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Discussion Starter · #9 ·
It does not have an odor, to me.

KNO3 has a molecular weight of 101.180 and K has a molecular weight of 39.0983:

39.0983 / 101.183 = 38.64% potassium
62.0817 / 101.180 = 61.36% nitrate
wait its supposed to be that high??
"Potassium nitrate is a water-soluble NK fertilizer containing 13.7% nitrate nitrogen and 46% potassium oxide (38.4%) " this is what's stated from the manufacturers of my KNO3

Can't comment on the test strips but KNO3 in solution should show up in reagent tests..

Make a reference solution and test..
I'm copying this in it's entirety since I found this is archived.
Those that are interested should c/paste for their own use.

will try this soon
 

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wait its supposed to be that high??
"Potassium nitrate is a water-soluble NK fertilizer containing 13.7% nitrate nitrogen and 46% potassium oxide (38.4%) " this is what's stated from the manufacturers of my KNO3
Different notation. It is stating it as nitrate-nitrogen (nitrogen in the form of nitrate). Nitrogen has a molecular weight of 14.0067, so 14.0067 / 101.183 = 13.8% nitrate-nitrogen.

Potassium oxide (K2O) has a molecular weight of 94.2, but note there are 2 potassium atoms in K2O. So, 94.2 / (2*101.183) = 46.55%
 

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Make a reference solution and test..
I'm copying this in it's entirety since I found this is archived.
I use 3000ml. However, I've been setting targets between the 5's, e.g.; 12ppm instead of 10ppm or 15ppm. Our test kits usually measure things on the 5's, so setting at, e.g.; 12, will tell me that I'm truly closer to 10ppm than 15ppm, depending upon the test kit. i also make up calibration mixes containing all measurable macros, so that I can store it all in one container. It also helps in calibrating my TDS meter.
 

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Discussion Starter · #12 ·
Different notation. It is stating it as nitrate-nitrogen (nitrogen in the form of nitrate). Nitrogen has a molecular weight of 14.0067, so 14.0067 / 101.183 = 13.8% nitrate-nitrogen.

Potassium oxide (K2O) has a molecular weight of 94.2, but note there are 2 potassium atoms in K2O. So, 94.2 / (2*101.183) = 46.55%
Different notation but does it mean the same thing? Im bad at chemistry lol so i barely know
 
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