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Discussion Starter #1
Currently I have a 55gallon low tech that is completly self sufficient now after adding some frogbit which sucked up all my nitrates so I'm not doing water changes at all really and I im starting to see potassium deficiencies in my frogbit and bocopa Carolina. So I figured it was because my well water was giving me the potassium I needed before but I just do top offs now so im wondering how much potassium should I be adding? I searched the forum and can't figure it out and I cant test it either so that doesn't help. So Thanks in advance for the help :)
 

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In general, we add potassium using two compounds, potassium nitrate and potassium sulfate.

If you want to add solely potassium, without adding nitrates, then you should use the latter compound.
 

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I currently have some K2so4 that I was going to use but what I was trying to figure out is how much to add that's what I'm confused on because now that I don't have to do water changes for a few months at a time I can't just get rid of it so I'll have a build up, I know it's not harmful when overdosed but Im just looking for a rough amount to start with and watch the results
 

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1 teaspoon of K2SO4 will put your tank into about the low end of mid-range for potassium needs. The problem is to know when to add more. When have the plants used up that dose? Unfortunately when you see holes in the leaves it is too late for those leaves. The holes won't heal when you dose more K.

Maybe you could figure it out from this. Remember that they want to sell as much as possible, so are probably suggesting the highest safe dose.

http://www.seachem.com/Products/product_pages/FlourishPotassium.html
 

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Discussion Starter #5
Thanks so much thats a place to start and i have a way to figure everything out after that so is not so bad. A week from now im going to take it to the chemistry lab and test the ppm and I can figure out my uptake. I talked to my chem teacher and he said he would let me use the lab and would help me test the water sample. Were going to use potassium premanganate and make a reference sample and then test the water sample and put it in a special machine to get the reading in ppm. I just thought that was cool since you can't really test for it.
 

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Instead of potassium you may want to consider Seachem Equilibrium. It contains potassium as well as calcium, magnesium, iron and manganese. Tom Barr created a post called the Non CO2 method and explains the concept including dosing suggestions. You may want to consider dosing the KNO3 and KH2PO4 since your Frogbit is utilizing your nitrates. It's only a matter of time until you see other deficiencies if you ignore this.

Here is a paragraph about dosing...

Quoted from - Non CO2 Methods

While trace mixes can be added, I decided to use SeaChem Equlibrium instead. It has Fe and Mn as well as Ca/K/Mg/SO4.
I will add about 1/4 teaspoon per 20 gal tank once every week or two.
This greatly enhances the growth of the plants.
I also will add about 1/8" and 1/32" teaspoon of KNO3 and KH2PO4 respectively once a week or two.
 
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