Fertilizer Calculation Confusion - The Planted Tank Forum
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post #1 of 8 (permalink) Old 12-01-2018, 01:23 PM Thread Starter
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Question Fertilizer Calculation Confusion

Fertilization questions

Iíve been using the base EI formula for macros and CSMB for micros based on the 60-80 gal formula. Recently upgraded my tank from a 75 to a 90, so Iíll need to update the fertilizer mix used.

My bottle is 500 ml but for ease of use, I had been filling it to 12oz mark, giving a full 4 week supply, adding 1oz at a time Ė 12 doses, simple.

KNO3: 2 1/4tsp per week, so 9tsp for 4wks
K2SO4: 9/16 tsp per week, so 2.25tsp for 4 wks
KH2PO4: 9/16 tsp per week, so 2.25tsp for 4 wks

I want to understand more about what Iím doing and having some control over the fertilizer mix in the tank. Iíd like to explore more about the fertilization and have seen numbers to shoot for based in ppm. With that it is obvious that switching to metric will make the calculations easier.

Iím really struggling with understanding how to use a calculator like Rotala Butterfly.

The part I understand:
Tank size 90 gals
My fertilizers are DIY
I can find the specific fertilizers I'm using ex KNO3
Container size 500ml
Dose size 30ml

What I don't get:

Target ppm

If for example, I input that Iím shooting for a specific level Ė does that imply the level per dose, or the total level for a week? Specifically, if the target is for 20ppm of Nitrate, what do I enter in the dosing for box? When I enter 20, the result is 9+ TBSP and I get a warning that the dose should be adjusted? Should it instead be entered as the daily dose (1/3 of the 20 ppm, or 6.67ppm)?

Elements contained in multiple fertilizers

The other thing that perplexes me involves Potassium, which is supplied by multiple mixes. KNO3 and K2SO4. In my head, it would be much simpler if Rotala allowed selection of multiple mixes. How should I establish a target, when clearly it is coming from multiple mixes?

I really feel that Iím completely missing the bus, as so many times it seems the answer is ďJust go to Rotala and it magically does the math for youĒ. I canít figure it out.
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post #2 of 8 (permalink) Old 12-01-2018, 02:01 PM
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I'll follow, I get confused by the rotala calc for the same reason, and so I am never 100% confident in how much K I'm dosing sometimes. Especially when I tried to figure out what to dose to preload my macros in my 20, so for now I'm still doing traditional EI

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post #3 of 8 (permalink) Old 12-01-2018, 02:35 PM
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Quote:
Originally Posted by nodim View Post
Fertilization questions

I’ve been using the base EI formula for macros and CSMB for micros based on the 60-80 gal formula. Recently upgraded my tank from a 75 to a 90, so I’ll need to update the fertilizer mix used.

My bottle is 500 ml but for ease of use, I had been filling it to 12oz mark, giving a full 4 week supply, adding 1oz at a time – 12 doses, simple.

KNO3: 2 1/4tsp per week, so 9tsp for 4wks
K2SO4: 9/16 tsp per week, so 2.25tsp for 4 wks
KH2PO4: 9/16 tsp per week, so 2.25tsp for 4 wks

I want to understand more about what I’m doing and having some control over the fertilizer mix in the tank. I’d like to explore more about the fertilization and have seen numbers to shoot for based in ppm. With that it is obvious that switching to metric will make the calculations easier.

I’m really struggling with understanding how to use a calculator like Rotala Butterfly.

The part I understand:
Tank size 90 gals
My fertilizers are DIY
I can find the specific fertilizers I'm using ex KNO3
Container size 500ml
Dose size 30ml

What I don't get:

Target ppm

If for example, I input that I’m shooting for a specific level – does that imply the level per dose, or the total level for a week? Specifically, if the target is for 20ppm of Nitrate, what do I enter in the dosing for box? When I enter 20, the result is 9+ TBSP and I get a warning that the dose should be adjusted? Should it instead be entered as the daily dose (1/3 of the 20 ppm, or 6.67ppm)?

Elements contained in multiple fertilizers

The other thing that perplexes me involves Potassium, which is supplied by multiple mixes. KNO3 and K2SO4. In my head, it would be much simpler if Rotala allowed selection of multiple mixes. How should I establish a target, when clearly it is coming from multiple mixes?

I really feel that I’m completely missing the bus, as so many times it seems the answer is “Just go to Rotala and it magically does the math for you”. I can’t figure it out.

Will give it my best shot to explain...
If for example, I input that I’m shooting for a specific level – does that imply the level per dose? * This implies level per dose. As an FYI, 20ppm of N from KNO3 per dose would be way too much. A weekly total of 20ppm of N from KNO3 would be much closer. Now comes the fun part - do you want to break that 20ppm into 3 doses? Or maybe into 5 doses where you give 2 doses just after water change, and 3 more doses throughout the week? Take your weekly goal of 20ppm and divide by say 3 and you get 6.6ppm. The standard EI recommendation is 7ppm.


The other thing that perplexes me involves Potassium, which is supplied by multiple mixes. KNO3 and K2SO4. In my head, it would be much simpler if Rotala allowed selection of multiple mixes. How should I establish a target, when clearly it is coming from multiple mixes? * For me, I use a spreadsheet. Others use a piece of paper - your choice. But, the answer to your question would be the K (potassium) from each different fertilizer does get added together. Hopefully the spreadsheet below gives you a little idea of what I am talking about. FYI, for the macros I am dosing the ferts "dry" and not in a mixed solution. But, the ppm per dose would be the same regardless of the dosing method. Another item of note - if you make a macro "mix", the amount you dose can make a big difference in whether or not the mixture will work. By that I mean, if you want to dose 1ml at a time and have a target of 20ppm N - the calculator will say no because the water can only dissolve so much of the fertilizer. If you want to dose 250ml at a time and have a target of 20ppm, then the calculator will not warn you. Takes a bit of time to figure out your dosing amount but you should only have to do it once.




Given the information you provided, your mixture - dosing might look something like below. This is based on EI recommendations

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Last edited by Immortal1; 12-01-2018 at 02:52 PM. Reason: <?>
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post #4 of 8 (permalink) Old 12-01-2018, 02:47 PM
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Quote:
Originally Posted by nodim View Post

What I don't get:

Target ppm

If for example, I input that I’m shooting for a specific level – does that imply the level per dose, or the total level for a week? Specifically, if the target is for 20ppm of Nitrate, what do I enter in the dosing for box? When I enter 20, the result is 9+ TBSP and I get a warning that the dose should be adjusted? Should it instead be entered as the daily dose (1/3 of the 20 ppm, or 6.67ppm)?

Elements contained in multiple fertilizers

The other thing that perplexes me involves Potassium, which is supplied by multiple mixes. KNO3 and K2SO4. In my head, it would be much simpler if Rotala allowed selection of multiple mixes. How should I establish a target, when clearly it is coming from multiple mixes?

I really feel that I’m completely missing the bus, as so many times it seems the answer is “Just go to Rotala and it magically does the math for you”. I can’t figure it out.
Target ppm; No one can answer this question for you. You ask five people on here and you'll probably get five different answers. EI dosing is a good starting point and was designed to take a lot of the guess work out of how much you should be dosing. The more time you spend messing with your own mixes the more you will probably come up with something that works in your tank. Most people that mess with mixing their own MACRO solutions do not venture to far off EI numbers, micros are a completely different story....

It's been so long since I actually used EI numbers but I think it 7.5N - 1.3P -7.5K. In the end, Rotata allows you to choose EI as a valve under "I am calculating for".

The above numbers are per dose. So if you follow EI and dose those numbers 3x a week, your totals at the end of the week would be 22.5ppm N - 3.9ppm P - 22.5ppm K.

Regarding Potassium (K), when you calculate the valve for KNO3, Rotala will spit out a K valve at the bottom. If you are dosing 7.5ppm KNO3 that valve will be 4.73ppm. Same goes for KH2PO4, if you are adding 1.3ppm per dose you'll be adding 0.54ppm of K as part of that dose. By adding the two numbers together we now know that we are already adding 5.27ppm of K every time we dose KNO3 and KH2PO4. Now to figure our how much extra K2SO4 we need to add to reach our target of 7.5ppm K we again just subtract 5.27ppm from our target of 7.5ppm. So we need to add an extra 2.23ppm of K2SO4 to reach our target of 7.5ppm K.

To figure this out you simple change the "I AM CALCULATING FOR" field on Rotala to Dose to reach a target. Enter your number of 2.23ppm and magically RB will spit out the number of grams of K2SO4 you need to add to get to your target of 2.23ppm.

I'll break it down.
7.5ppm of KNO3 supplies 4.73ppm K
1.3ppm of KH2PO4 supplies 0.54ppm k
Together they add 5.27ppm K
We want to add a total of 7.5ppm K per dose
So we need to add an extra 2.23ppm K per dose to reach our target of 7.5ppm K per dose.

Picture is just an example to show the K valve when dosing 7.5ppm of KNO3. Your gals, container size and dosing size maybe different.


Let me know if any of this makes sense...... If not I can try and walk you through mixing a batch if you like.
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post #5 of 8 (permalink) Old 12-02-2018, 01:59 PM Thread Starter
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Thanks Immortal and Slipfinger - that should open the door for me now, I see where my confusion happened.

Going to do some playing around and go from there. Also just created a journal in the journal subforum.

Thanks again.
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Last edited by nodim; 12-02-2018 at 05:46 PM. Reason: edit
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post #6 of 8 (permalink) Old 12-02-2018, 02:22 PM
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One thing to keep it mind:

In slip's screenshot above, it lists NO3, N, and K as the breakdown from adding KNO3.

The NO3 and N are the same thing.

7.5ppm of Nitrate (NO3) has 1.69ppm of Nitrogen (N) contained within it.

The calculator does the same thing with KH2PO4 - lists the ppm in PO4 as well as the equivalent of straight P.
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post #7 of 8 (permalink) Old 12-06-2018, 12:50 PM
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I know this is a few days old but I thought I'd offer up a tool to help out. A while back ( a few years) I had similar questions and wrote an Excel spreadsheet to work it all out. I recently revisited it and back checked it against Rotala and, at least for the major EI and PPS components it matches up. It will work with the open source application LibreOffice.

It will breakout the individual elements (just like Rotala) but it also totalizes them and calculates a weekly dose based on the individual dose and the number of doses per week. It also allows for removing individual componets from the solution to be front loaded weekly and calculates the weekly front load dose. Solubility calculations are made as a guideline.

I started a thread for it a while back and got crickets.

https://www.plantedtank.net/forums/1...l#post11137451

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post #8 of 8 (permalink) Old 01-03-2019, 06:59 AM
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hi,

I am Ardhendu from India.
Please tell me DIY formula for Fertilizer, Algae remover And Liquid CO2.

Thanks In Advance for your Help and suggestion.

Regards,
Ardhendu
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