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Discussion Starter · #1 ·
How many drops of KNO3 (2 teaspoons mixed in with 167ml of H2O) should it take to give 9L of water about 5ppm of NO3? I think my test kit is stuffed as I have put 30 smallish drops in and the kit (Nutrafin) tells me it has less than 5 ppm! Could this be right?
David
 

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2 teaspoons or approx 8.5g of KNO3 mixed in 167ml water will make a solution where 1ml or 20 drops will raise N level 3.54ppm so 30 drops would be 5.31 ppm. I'd check the test kit.
 

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Here is a great tool for plant tank enthusiasts. Many of us here use it when calculating our doses. The Fertilator located at the top of Aquatic Plant Central is also very nice:) Try them both. You might find it easier or more accurate to dose a more nominal size like 1 liter or 1 gallon, something along those lines. Also, grams are more accurate than tsp, which are simply a rounded estimate based on grams anyway.

For instance, 0.03grams KNO3 in 1 gallon H2O is ~4.6ppm NO3. 0.03grams is about .01 teaspoons. That is maybe equal to the amount of KNO3 you would need to cover an period in a regular newspaper article. You can see why it is hard to check with small tests:) You would be beter off dosing a 5 gallon bucket or something. If you know how much you add to your tank. Dose that amount and then test in 1/2 hour. HTH:)
 

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Use the Salt water colour table for the NO3 Nutrafin Hagen test. I tested it with standard solutions 0, 5, 10, 20 and 30 ppm, and it does read right on with the Salt water colour table.

Edward
 

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Discussion Starter · #5 ·
Thanks for the link, I think i may need to get another test kit. in the meantime Ive done some thinking and found chucks calculator, put it to use and came out with the thought that I would need a about 1ml of the KNO3 mix for 9L H2O and that would give me about 4.57ppm.

2 teaspoons ~ 11.2g KNO3 (chucks calculator)
11.2g KNO3 / 167mL = 0.067g KNO3 per 1mL of mix
so
0.067g of KNO3 mixed with 9L H2O would be 4.57ppm by chucks calculator

simple I thought. Wrong :(
if i use the math that Rolo used at this post
http://www.aquaticplantcentral.com/forum/viewtopic.php?t=2621
and modify it to this

Molar mass KN03 = 101.1g
Molar mass N = 14.0g

For 1L H2O
0.033g KNO3 x (14.0g/101.1g) = 0.00457g N = 4.57 mg N
1000mL = 1L
4.57mg/L = 4.57 ppm N

So for 9L H2O
0.033g x 9 = 0.297g
0.297g KNO3 in 9L = 4.57 ppm

That's 4 or 5 times as much as chucks calculator states :shock: !! Where am I wrong?
Turtle
 

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You forgot about Oxygen to include in your second calculation. We test for NO3, not for N.

KNO3 -> (38.7% K, 13.9% N, 47.5% O)

61.4% of NO3 in KNO3

There is nothing wrong with the Hagen Nutrafin NO3 test. I tested Aquarium Pharmaceuticals NO3 kit and found the same thing. The Salt Water colour table is right for fresh water measurements.

Edward
 

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Discussion Starter · #7 ·
A slight over look on my part :oops: thanks for the help edward it is greatly appreciated, i will do a controlled test with the kit now that i have some idea of what it should take to get 5ppm, no doubt it will be right [-o<

David
 

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2 teaspoons ~ 11.2g KNO3 (chucks calculator)
and in my post I said

2 teaspoons or approx 8.5g
Edward and I were discussing this in chat and I went and weighed a tsp of KNO3 10 times using a standard kitchen measureing spoon set. The avg of 10 seperate entries was 4.34g. That comes to a bit more then 1 gram less then Chuck's.

Just a point of reference
 
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