dry dosing KS204 - The Planted Tank Forum
Old 01-04-2009, 05:58 PM Thread Starter
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dry dosing KS204

I've been using the flourish line for about a year now and in the process of switching to dry dosing. I think I've figured out the mixtures for the N.P. and trace but I have questions for K.

I want to adjust all my mixtures so that I can dose 4 ml of each chemical.
I used chucks calculator to get my numbers

But I'm a little concerned about the numbers that I got for
Potassium. but before I get into that, let me say that I mixed the Potassium and water using the number I got from the calc and then read online that I shouldn't mix it with water. Dry dosing it is easier.
Since it's too late for that now, I'm forced to use the batch I made up.
The problem (I think) is that the calculator says I should mix 15 TBS KS204 to 500 ml of water. So each ml of solution will raise my K by 1.69ppm.
Sticking with my 4 ml dosing target I get 6.76 ppm per dose 3x week for 20.28 ppm per week.
Here's my delema (sp)

15 TBS seems like an awful lot of Potassium for 500 ml of water.
from what I read online 1/4 tsp raises potassium in a 10 gal tank by
16 ppm (or so).

can someone reassure me that I'm not going to seriously overdose my Potassium using this math. this was calculated for a 38 gal tank btw.
Thx

Last edited by plant_killer; 01-04-2009 at 08:29 PM.
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Old 01-04-2009, 06:21 PM
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The calculator was giving me the same results as yours.

If you were just going to add it dry to the tank you would add about 1/3 tsp to give the about 6.25ppm

The problem I encountered with you plan was that the calculator said you can't dissolve that much potassium sulfate in that much water. In fact its saying you can only dissolve about 1/5th (3 1/3 TBS) that in 500ml

If you were doing full EI you want to add 20ppm of potassium each dosing day not 20ppm over the week total.

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Old 01-04-2009, 06:30 PM
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In EI the majority of Potassium comes from the KNO3 with some additional coming from the KH2PO4. There is some flux with the issue of dosing K2SO4. The current thinking is that one should add GH booster after the weekly water change to bolster Ca, Mg, and K levels and not to dose additional K throughout the week with the N & P.

K2SO4 has extremely limited solubility, there's no chance you'll get 15 TABLESPOONS to dissolve in 500 ml of water. The maximum solubility is only 11.1 g per 100 ml of water at 20 degrees C.

There is no need to reinvent the wheel here. You can dose EI levels using liquid by following this recipe directly from the source of the method: http://www.barrreport.com/estimative...ei-dosing.html

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Old 01-04-2009, 06:32 PM Thread Starter
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You are correct
That much potassium does not dissolve in water. It sinks to the bottom.
I was thinking I could just shake the bottle before I dose.
Where did you see that it won't dissolve that much, I didn't see that

this is where I got the 20 ppm per week thingy

Note: This is not the amount you should add per ml, but rather this is the total level you should target for the tank. For nutrients like Potassium and magnesium, I add enough so that each week, I'm adding close to this amount. For Nitrates, you should adjust your dosage based on the results of a nitrate test kit, to achieve the desired PPM
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Old 01-04-2009, 06:38 PM Thread Starter
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imeridian

Does this mean that I don't even need KS204 so long as my tap is ok?
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Old 01-04-2009, 06:41 PM
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I'm saying that the current EI plan calls for using GH booster weekly instead of dosing K separately during the week. The plan suggests enough GH booster to increase GH by one degree, this serves the purposes of making sure you have enough Ca, Mg, and K -- even if you consider your water to be hard.

If you have hard water and want to disregard that portion of the plan being confident you have sufficient Ca & Mg, you could instead just toss in a dry 'slug' of K2SO4 after the weekly water change. That may also be unnecessary, but the idea behind EI is that you ensure there are no deficiencies of any element by supplying all of them.

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Old 01-04-2009, 06:47 PM
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Quote:
Originally Posted by plant_killer View Post
You are correct
Where did you see that it won't dissolve that much, I didn't see that
If you are in the calculator and do something that it thinks will not work red text pops up on the right side and will give you some sort of advice.

You could calculate out how much K is coming from KNO3 and adjust your levels from there. The calculator also has this option.

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