Switching fert methods - concentration/math help - The Planted Tank Forum
Old 07-28-2014, 07:27 PM Thread Starter
Algae Grower

Join Date: Jul 2011
Location: Central AZ
Posts: 81
Switching fert methods - concentration/math help

I'd like to switch from PPS-Pro to EI. The thing is, I don't want to toss the solution that I have b/c I don't have a lot of ferts left and am not sure when I'll be able to get more.

Here is how I made my solution initially:
Macro Solution
In 1 liter bottle:
59 grams K2SO4
65 grams KNO3
6 grams KH2PO4

Trace Solution
In 1 liter bottle:
80 grams of Plantex CSM+B

At first, I thought I could just add the extra amounts for EI. But one bottle is about 3/4 full and the other is only 1/2 full (because I spilled it ).

So I used a calc and figured out that in each dose (1 mL of each solution) there is:
39.8645 mg NO3
53.3326 mg K
4.1874 mg PO4
1.120 mg Mg
5.224 mg Fe
At least I think that's what it is.

Anyway, I've fried my brain trying to do all sorts of weird math. How can I figure out what amounts of each chemical I need to add in order to get these nutrient concentrations?
NO3 7.5 ppm
N 1.694 ppm
PO4 1.3 ppm
P 0.424 ppm
K 5.3 ppm (7.5 ppm with additional K2SO4)
Fe 0.5 ppm
Mg 0.107 ppm
dGH 0.025 ppm
Cu 0.007 ppm
B 0.061 ppm
Mn 0.143 ppm
Mo 0.004 ppm
S (0.917 ppm with additional K2SO4)
Zn 0.028 ppm

quietdusk is offline

Old 07-29-2014, 01:33 AM
Planted Tank Guru

Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,015
If you want to switch to the EI method, you wont be concerned with exact amounts of each of the fertilizers. When you aim at specific goals for each fertilizer concentration in the tank water you are not using the EI method.

Hoppy
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Old 07-29-2014, 05:06 AM
Planted Tank Guru

Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721

1) Figure out how much fertilizer your tank needs in a week. (use the EI chart stickied at the top of the Fertilizer Forum)
a) Macros: N, P, K
b) Micros: All the traces, Fe
c) Other (in case you need to dose GH booster more often than with water changes)

2) Figure out how many doses you have in your bottle. For example, a 1 liter bottle might be dosed at 1ml/3 gallons, in a 30 gallon tank and so use 10ml per dose, so 100 doses in the bottle. This is not too far off a 3 month supply. (3 doses per week)
so, put 3 months worth of fertilizer in the bottle, fill with water. Shake well.
You will have to do the math depending on what size your tank is.

I find that dosing at 1 ml per 3 gallons is about as concentrated a solution as I can make. I need to shake well each time I use it.

Then, go back to the blends you already made. Are any of them close to what you just figured out?
Pretty close? or Not too far off? Use them as is, and monitor the tank.
Way out there? Add more of what is missing until it is at least somewhat closer. Monitor the tank. After about 1-2 weeks see if you need to do more adjustments.

Note that the EI method assumes you are running a high tech tank. It doses all KNO3 as a source of potassium. If your tank does not need that much NO3, but does need that much potassium, then dose only enough KNO3 to provide NO3, and use K2SO4 for the additional K. I am running low tech tanks, and dosing about the same amounts of KNO3 and K2SO4 so the NO3 does not climb so fast. Looks like you started to do something similar.
Diana is offline

Old 07-29-2014, 12:36 PM
Planted Tank Guru

Join Date: Jun 2012
Location: Gainesville, FL
Posts: 2,105
PPS-Pro uses less phosphates. So your macro bottle needs more KH2PO4. To bring the solution (1 liter) to EI levels add 4 grams of KH2PO4 to you macro bottle. You didn't mention which bottle was 3/4 or 1/2 full. If the macro bottle is half full add 2 grams of KH2PO4. If it's 3/4 full add 3 grams. That solution should be dosed at 7ml per 10 gallons 3 times a week with a 50% water change every week. That dose is for high light with CO2 injection.

You didn't need the K2SO4 since KNO3 provides enough. It shouldn't cause an issue just mentioning it for future solutions.

Use you micro bottle as is. Dose 3 1/2 ml per 10 gallons 3 times a week.
Zorfox is offline
Old 07-29-2014, 07:56 PM Thread Starter
Algae Grower

Join Date: Jul 2011
Location: Central AZ
Posts: 81
How cool! I got replies from 3 of the 4 ppl who's posts I've been reading lately

Quote:
Originally Posted by Hoppy View Post
If you want to switch to the EI method, you wont be concerned with exact amounts of each of the fertilizers. When you aim at specific goals for each fertilizer concentration in the tank water you are not using the EI method.
I actually read one of your posts about EI being more of a concept than strict rules. It's what prompted me to look into it more!
I just wanted to figure out what I already had in my solutions so I could get a general idea of what to change up.

Quote:
Originally Posted by Diana View Post

1) Figure out how much fertilizer your tank needs in a week. (use the EI chart stickied at the top of the Fertilizer Forum)
a) Macros: N, P, K
b) Micros: All the traces, Fe
c) Other (in case you need to dose GH booster more often than with water changes)

2) Figure out how many doses you have in your bottle. For example, a 1 liter bottle might be dosed at 1ml/3 gallons, in a 30 gallon tank and so use 10ml per dose, so 100 doses in the bottle. This is not too far off a 3 month supply. (3 doses per week)
so, put 3 months worth of fertilizer in the bottle, fill with water. Shake well.
You will have to do the math depending on what size your tank is.

I find that dosing at 1 ml per 3 gallons is about as concentrated a solution as I can make. I need to shake well each time I use it.

Then, go back to the blends you already made. Are any of them close to what you just figured out?
Pretty close? or Not too far off? Use them as is, and monitor the tank.
Way out there? Add more of what is missing until it is at least somewhat closer. Monitor the tank. After about 1-2 weeks see if you need to do more adjustments.

Note that the EI method assumes you are running a high tech tank. It doses all KNO3 as a source of potassium. If your tank does not need that much NO3, but does need that much potassium, then dose only enough KNO3 to provide NO3, and use K2SO4 for the additional K. I am running low tech tanks, and dosing about the same amounts of KNO3 and K2SO4 so the NO3 does not climb so fast. Looks like you started to do something similar.
Thanks for the step-by-step.

Quote:
Originally Posted by Zorfox View Post
PPS-Pro uses less phosphates. So your macro bottle needs more KH2PO4. To bring the solution (1 liter) to EI levels add 4 grams of KH2PO4 to you macro bottle. You didn't mention which bottle was 3/4 or 1/2 full. If the macro bottle is half full add 2 grams of KH2PO4. If it's 3/4 full add 3 grams. That solution should be dosed at 7ml per 10 gallons 3 times a week with a 50% water change every week. That dose is for high light with CO2 injection.

You didn't need the K2SO4 since KNO3 provides enough. It shouldn't cause an issue just mentioning it for future solutions.

Use you micro bottle as is. Dose 3 1/2 ml per 10 gallons 3 times a week.
Thank you for this! You answered my question exactly. I finally figured out how to use the fert calculators (who knew there were so many options in those drop-downs??). I was struggling with finding the right balances, though.

So how do you figure out all of these numbers? I'm assuming you first find out which nutrient is the most limiting for plants and figure out how much you need of that, then calculate the nutrients in that amount of fertilizer, and finally add the amounts of other fertilizers needed to surpass the limits of the other nutrients.
But how do we know(assume) what the nutrient limits are? Is there a chart somewhere?

And I have a question about Fe. I have a bottle of API Leaf Zone, which is chelated with EDTA. I think I read that was the most stable form. Should I use that in conjunction with my trace or not worry about it?

Thanks for everyone's help. I'd really like to learn as much as possible so that I can eventually figure this stuff out for myself. lol.
quietdusk is offline
Old 07-29-2014, 08:12 PM Thread Starter
Algae Grower

Join Date: Jul 2011
Location: Central AZ
Posts: 81
Oh, and thank you for reminding me that the dosages are for high tech, Diana.
I read that for low light and no CO2, the dosage should be reduced to 1/3. For medium light and DIY CO2, would 1/2 dosage be better?
quietdusk is offline
Old 07-29-2014, 10:56 PM
Planted Tank Guru

Join Date: Jun 2012
Location: Gainesville, FL
Posts: 2,105
The amounts for each nutrient are listed below. Those are the ranges Tom Barr has arrived at through years of testing. No need to reinvent the wheel.

You don't need to use API leaf zone if you're using Plantex. Plantex has EDTA iron.

Did you get the 1/3 from this thread? If so, that's for tanks using Excel. In fact the real number would be around 10% of full EI. No CO2 and low light? Far lower than that.

If you're doing 50% weekly water changes per the EI method there is really no need to get too specific about how much the plants will use. In reality you can dose full EI with low light and no CO2 although it's simply not necessary.

It's hard to say how much with DIY CO2. So to be safe I would personally dose full EI if you have high light and do the 50% water change. Then you can reduce the dosage over time until you see problems.

These are from this thread, The Estimative Index of Dosing, or No Need for Test Kits.
Quote:
(+ or -) 5ppm of CO2 is fine in a 20-30ppm range.
(+ or -) 1ppm or so of NO3 is pretty reasonable.
(+ or -) 2ppm of K+ is pretty reasonable.
(+ or -) 0.2ppm of PO4 is pretty reasonable (?)
(+ or -) 0.1ppm of Fe is reasonable (?)

CO2 range 25-35ppm
NO3 range 5-30ppm
K+ range 10-30ppm
PO4 range 1.0-3.0 ppm
Fe 0.2-0.5ppm or higher (?)
GH range 3 degrees ~ 50ppm or higher
Zorfox is offline
Old 07-30-2014, 12:53 AM
Planted Tank Guru

Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721
Do one or the other, monitor conditions and alter as needed.
I used the 'half' because the range of EI was for tanks from 20-40 gallons.
It seems to me that if a 40 gallon low tech and a 20 gallon high tech would use the same sort of formula, then a general, rough guide is that a low tech uses half the ferts of a high tech.

None of this is cast in stone. Try it. Make about 2 weeks worth and see how it goes. Alter as needed.
Diana is offline
Old 07-30-2014, 01:52 AM Thread Starter
Algae Grower

Join Date: Jul 2011
Location: Central AZ
Posts: 81
Great info! Thanks again!
quietdusk is offline

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