where can I find the exact calculations used to figure out dosing routine? - The Planted Tank Forum
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post #1 of 9 (permalink) Old 09-05-2016, 01:31 PM Thread Starter
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where can I find the exact calculations used to figure out dosing routine?

I am trying to get more into the nitty gritty of tank maintenance and control. I see a number of wonderful calculators out there, but they all, obviously, hide away the specifics.

As a programmer, I like to see how things work to better understand how to use them.

I understand what the basic equation to get PPM is. But I also understand that that basic equation is not what a number of people are using, I read something about molar mass in my initial research.

And then of course, we're only, perhaps in this example, concerned about the NO3 portion of KNO3, so wish to only find that portions PPM in a 1000ml solution.

I'd like to pierce through the "magic veil."


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post #2 of 9 (permalink) Old 09-05-2016, 02:51 PM
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Dosing is really just an estimate. You don't need to worry about "exact" calculations. If you were, you would be changing your dosing routine every single day since the tank is changing every day in terms of uptake, waste, co2, plant mass, PAR etc.

That's why it's an Estimative Index
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post #3 of 9 (permalink) Old 09-05-2016, 03:00 PM Thread Starter
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Quote:
Originally Posted by houseofcards View Post
Dosing is really just an estimate. You don't need to worry about "exact" calculations. If you were, you would be changing your dosing routine every single day since the tank is changing every day in terms of uptake, waste, co2, plant mass, PAR etc.

That's why it's an Estimative Index
I appreciate the response, but I am asking for the exact equations used to figure out the dosing routine. specifically in regards to how to calculate the PPM of a solution, and of specific portions of a chemical, such as KNO3. and then only the NO3.

It's not that I want to precise exact required numbers for the sake of actual dosing, but I am interested in the equations/formulas used to answer, "how many grams of kno3 do I need in a 1000ml solution, while dosing my tank at 20ml to achieve the desired range of PPM in the aquarium itself?"

The calculators are obviously out there that answer the question, but I want to know the formulas they're using to answer the question.
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post #4 of 9 (permalink) Old 09-05-2016, 05:09 PM
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Here is some help, I hope.

You need a chart for one, that contains elements and compounds of our interest.
It should be titled "Grams per 100liter to equal 1 ppm"

KNO3 example as follows.
Lets say you are making a dosing bottle of 500ml.
Adding 4 grams of KNO3 to it and want to know total ppm of KNO3 in the dosing bottle.

(4/.1631)*(100000/500)=4905ppm

.1631 is from the chart for NO3.

Potassium on the chart is .2586

Solve for K (4/.2586)*(100000/500)=3094ppm

Here is one of such charts I know off.
Not secret information for sure.
At the bottom are some chemical tables.
https://sites.google.com/site/aquati...home/chemicals

This chart does not include all of the things we use as aquarists.
You can look up specific compounds and find info.

Microsoft Excel is your friend on this one.


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post #5 of 9 (permalink) Old 09-05-2016, 05:40 PM Thread Starter
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Quote:
Originally Posted by Maryland Guppy View Post
Here is some help, I hope.

You need a chart for one, that contains elements and compounds of our interest.
It should be titled "Grams per 100liter to equal 1 ppm"

KNO3 example as follows.
Lets say you are making a dosing bottle of 500ml.
Adding 4 grams of KNO3 to it and want to know total ppm of KNO3 in the dosing bottle.

(4/.1631)*(100000/500)=4905ppm

.1631 is from the chart for NO3.

Potassium on the chart is .2586

Solve for K (4/.2586)*(100000/500)=3094ppm

Here is one of such charts I know off.
Not secret information for sure.
At the bottom are some chemical tables.
https://sites.google.com/site/aquati...home/chemicals

This chart does not include all of the things we use as aquarists.
You can look up specific compounds and find info.

Microsoft Excel is your friend on this one.
should the 100000 in your equations be 1000000? is one hundred thousand correct?

This is definitely moving in the right direction.

So this would give me the PPM within a solution. What specifically is .1631 though? Is that 1g of KNO3 into 100 liters of solution is .1631ppm of KNO3? How is that "base" PPM calculated?

I like seeing the solubility on there as well. I'm always amazes when my 100+ grams of KNO3 dissolve into 1000ml, but it appears that I could dissolve 350g of it, so it makes sense now that it will dissolve just fine.


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post #6 of 9 (permalink) Old 09-05-2016, 06:11 PM
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Quote:
Originally Posted by scapegoat View Post
should the 100000 in your equations be 1000000? is one hundred thousand correct?

So this would give me the PPM within a solution. What specifically is .1631 though? Is that 1g of KNO3 into 100 liters of solution is .1631ppm of KNO3? How is that "base" PPM calculated?

I like seeing the solubility on there as well. I'm always amazes when my 100+ grams of KNO3 dissolve into 1000ml, but it appears that I could dissolve 350g of it, so it makes sense now that it will dissolve just fine.
One hundred thousand is correct, don't remember why.
I solved this for the spreadsheet quite some time ago.
Need to look up and refresh my old mind.

.1631 grams per 100 liter to reach 1ppm
This is only relative to NO3 in KNO3 as a compound.
The K, N, and O can all be calculated as separate elements.

Solubility would be another chart required for spreadsheet comparisons.
Tough dissolvers are CaCO3, CaSO4, etc...
I still mix them in a small container even though it is a suspension.
Having to shake before measuring.

Did you find the charts?

Spent way too much spreadsheet/formula time when first starting out.


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post #7 of 9 (permalink) Old 09-06-2016, 04:25 AM
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My apologies. It is late. I hope this makes sense. I don't hardly understand the table mentioned above. This is the way I do it.

ppm = mg/L

1 ppm = 1 mg/L

1000mg = 1gram (g)

therefore
1gm in 1L = 1000mg/1L = 1000ppm
1gm KNO3 in 1L = 1000mg/1L = 1000ppm KNO3

The question is then, if you put 1gm of KNO3 in 1L of water, how many ppm of NO3 do you have. To find the answer, you have to use the periodic table and the weights of the elements. I am rounding for simplicity

I used this one:
Dynamic Periodic Table

K = 39
N = 14
O = 16 but remember it is O3 so for our sake O = 48

Total KNO3 = 101
Total NO3 = 62
62/101 = 0.614 = 61.4%

This mean 61.4% of KNO3 is NO3
Therefore if you put 1000mg of KNO3 into 1L of water, and 61.4% of it is NO3, then for every 1000mg of KNO3 you are putting in 614mg of NO3 and you have 614ppm NO3

You can check this by going to a fertilizer calculator like this one.
Rotala Butterfly | Planted Aquarium Nutrient Dosing Calculator

Say your aquarium is 1L because that is your final volume
DIY
You are DRY dosing with KNO3
You are calculating for “result of my dose”
You are adding 1gm
Limit to 2 decimal places

Calculate: You get 613ppm (If you got 162ppm you forgot to change from gallons to liters)

Just for fun then:

How many ppm NO3 do you have if you put 1gm KNO3 into a 10 gallon aquarium. (empty except for water of course)
1 gallon is about 4L
10 gallons = 40L
1gm KNO3 has 614mg NO3 (established above)
614mg NO3/40L = 15.35mg/L = 15.35ppm

Last edited by Ben Belton; 09-06-2016 at 02:14 PM. Reason: Corrected the wt of O
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post #8 of 9 (permalink) Old 09-06-2016, 01:51 PM Thread Starter
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@Ben Belton that helps very very much. And greatly simplifies the process in my mind.

Where are you getting O = 24 though? I am seeing 15.999. The other two are correct.

I was also under the impression that there needed to be a conversion of water to molar mass as well? Now, I can't begin to tell you where I saw that, it may be my own failed thought process.

Otherwise, your explanation is perfect and simple. Thank you very much.


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post #9 of 9 (permalink) Old 09-06-2016, 02:12 PM
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Quote:
Originally Posted by scapegoat View Post
Where are you getting O = 24 though? I am seeing 15.999. The other two are correct.
Sorry. O = 48 which is 16 x 3. The math should (I hope) still be correct though. I did it on a piece of paper before I wrote my reply. I just copied the numbers wrong.

I will correct it above.

Quote:
Originally Posted by scapegoat View Post
I was also under the impression that there needed to be a conversion of water to molar mass as well? Now, I can't begin to tell you where I saw that, it may be my own failed thought process.
I'm not sure about that. You shouldn't have to convert water into anything. Maybe it came from the discussions of solubility above.
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