# Potassium To Nitrate Ratio?



## Highseq (Jul 26, 2017)

Teebo said:


> I know the naturally occurring potassium level is much lower than nitrate but what kind of ratios are we talking about? I ask this to find out the minimal nitrate range that will have free/usable potassium.
> 
> I have one heavily planted tank that eats everything in the water column, and requires weekly dosing of everything including nitrate/nitrogen. I dose it up to about 5ppm and it drops to almost 0ppm by the end of the week. Then I have my Iwagumi tank which hovers around 15-20ppm nitrate, so I do not dose nitrogen in this tank but I do dose potassium weekly, which I think is the secondary most consumed nutrient by algae as well. Based on 15-20ppm of nitrate I am trying to estimate if that would have at least a natural 1-2ppm potassium, the key is having just enough the plants can use. I play this line in my heavily planted tank, as long as I have 1-2ppm nitrate left by the end of the week nothing turns yellow and my glass stays free of algae.


I have seen multiple of tom barr's posts saying it is the least toxic of NPK in terms of toxicity. You can basically keep it at a 1:1 ratio with your nitrates. I think EI doses around 2-3ppm per day if i am not mistaken, so about 14-20ppm per week.


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## Teebo (Jul 15, 2015)

I realize its not toxic, but why keep it higher than needed by your plants if its only going to feed algae? Its the ratio I am trying to determine to keep it low as possible. They say an iron test can help with EI for all nutrients but I am not testing for iron so I have to rely on nitrate levels. I see no point in dosing potassium weekly if 15-20ppm of nitrate means there is free usable potassium available.


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## happi (Dec 18, 2009)

Highseq said:


> I have seen multiple of tom barr's posts saying it is the least toxic of NPK in terms of toxicity. You can basically keep it at a 1:1 ratio with your nitrates. I think EI doses around 2-3ppm per day if i am not mistaken, so about 14-20ppm per week.


i would love to see where he have stated about toxicity, that would be interesting for me.


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## jeffkrol (Jun 5, 2013)

Potassium in "excess" is apparently not a problem...


> Been this way for nearly 15 years............still think high PO4 causes algae or might it just be something else that you or friends, or those you are talking to overlooked?
> 
> I know I'm adding pure bioavailable PO4 in the form of KH2PO4 into the water column.
> 
> ...


http://www.plantedtank.net/forums/11-fertilizers-water-parameters/61625-potassium-deficiency.html



> K is not typically a problematic nutrient. I have had 20,30,40,60,80 and 100+ K ppm levels in my tanks with no issues. The highest I did was 150 ppm K and this was tested by a laboratory. On Average, I keep my K levels around 40-60 ppm (high tech tank) and not worry about it too much. Usually if the Ca/Mg levels are higher then I try to keep my K higher too. Like what Django suggested, you can dose for the target K after a water change and forgot about it.
> 
> Typically the K levels will get higher if you are dosing KNO3 and KH2PO4.


http://www.plantedtank.net/forums/1...ameters/1100698-k2so4-potassium-question.html


http://aquarium-fertilizer.com/potassium-k



> Some of the potassium is contained in fertilizers like Potassium Nitrate (KNO3) and Monopotassium Phosphate (KH2PO4) but it’s a smart idea to add some extra potassium from Potassium Sulphate (K2SO4).
> 
> If you are using as a fertilizer KNO3, you should add the same amount of Potassium Sulphate (K2SO4). Example:
> 
> If you are using for your 25 gallon tank 1/2 tsp of KNO3 weekly, you should use also 1/2 tsp of K2SO4 weekly. If you’re not using KNO3 because you have enough of nitrogen (N) in your tank, you can just use 1 tsp of K2SO4 instead.


About that algae........
http://aquarium-fertilizer.com/nitrate-no3-and-phosphate-po4-dont-cause-algae-ammonia-does



> How we said before, algae spores want ammonia (NH4) and algae needs nitrate (NO3). You are reading this article probably late, because your algae spores became regular algae. But don’t worry. You can still fix it. You have to start adding nitrate (NO3), phosphate (PO4) and all other important nutrients including CO2. It doesn’t make any sense? No, it makes sense. You have to care about your plants, because they aren’t in a good shape right now. Old leaves produce ammonia (NH4) and algae spores become an algae. Fertilizing will cause that your plants will be in a good shape and they won’t produce more ammonia (NH4) so there wont’t be a new algae. Additionaly, healthy plants will eats ammonia so algae spores will suffer. On the other hand, algae which is present in aquarium right now will be grow because it is full-grown algae which eats nitrate (NO3). Yeah, that’s true, but you will remove it after a while and there won’t become another one, because you removed ammonia, so no other spores will become an algae. Pretty cool, isn’t it?
> 
> If there is an algae bloom in your tank, and you will cut the dosage of fertilizer down, it is the worst you can do because your plants will suffer from lack of nutrients, their leaves will be unsightly and will cause ammonia (NH4) -> algae. Plants have to be healthy, only in that case algae won’t be present in your tank!


https://www.google.com/url?sa=t&rct...in.pdf&usg=AFQjCNHaxgNsrYfHZUah6M3yMJbZTi9Tsg


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## dukydaf (Dec 27, 2004)

Teebo said:


> I know the naturally occurring potassium level is much lower than nitrate but what kind of ratios are we talking about? I ask this to find out the minimal nitrate range that will have free/usable potassium.
> 
> Based on 15-20ppm of nitrate I am trying to estimate if that would have at least a natural 1-2ppm potassium, the key is having just enough the plants can use. I play this line in my heavily planted tank, as long as I have 1-2ppm nitrate left by the end of the week nothing turns yellow and my glass stays free of algae.





Teebo said:


> I see no point in dosing potassium weekly if 15-20ppm of nitrate means there is free usable potassium available.


I am curious as to why do you focus on the ratio of NO3:K ? Why not a ratio of two cations like K:Ca ? Isn't that more likely to cause problems? And what kind of ratio are you targeting? molar ? mass ?

The problem with this NO3: K ratio is that you can have one without the other. In "naturally occurring" systems, most of the NO3 comes from the breakdown of amino acids, NH3... In all our aquariums, a similar processes happens. This means that you are always adding NO3 without adding any K. If you want a more controlled way to increase your NO3 you can add small amounts of urea or Ca(NO3)2. 
You see the problem here ? 15-20ppm NO3 might mean just as well you have ~0ppm K in plant available form. 

While yellow leaves are a sign of severe N starvation, you can see a large decrease in plant biomass production coming from nitrogen limitation alone. Good thing our plants are able to adapt so well :smile2: I don't want to discourage you from trying, maybe you come up with a new system. Just curious about your thoughts. 

However, about ratios in general, I will stop at this thought. The atmosphere of Earth has 20.9% O2 and 0.0407% CO2 (wiki values). This gives a ratio of ~513:1 O2:CO2 by volume. You will have the same ratio if Earth's atmosphere were 2.09% O2 and 0.00407 CO2%. Will you be able to breathe just because the ratio of O2:CO2 has not changed ?:angel::angel::angel:


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## Teebo (Jul 15, 2015)

My ratio thoughts have nothing to do with toxicity at all, I have already stated my reasoning and it was answered here: "15-20ppm NO3 might mean just as well you have ~0ppm K in plant available form."

I will continue adding Potassium to my tanks that have higher levels of Nitrate. The reason I did not mind low nitrate levels is because in an established tank it keeps trimming maintenance low, why dose just to trim if its filled out the way you want it? Long as it stays green the way it was I was happy.


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## rhiro (Sep 21, 2012)

Teebo said:


> My ratio thoughts have nothing to do with toxicity at all, I have already stated my reasoning and it was answered here: *"15-20ppm NO3 might mean just as well you have ~0ppm K in plant available form*."


I have never seen this statement anywhere in all the planted tank/aquascaping literature I have read. Could you advise where you got this information?


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## roadmaster (Nov 5, 2009)

rhiro said:


> I have never seen this statement anywhere in all the planted tank/aquascaping literature I have read. Could you advise where you got this information?


Would only be true if you also omitted KH2PO4,K2SO4, from dosing scheme.
Could have xxppm NO3 from tap maybe, and not need KNO3.
Perhaps some clarity as to difference between NO3 and KNO3 is needed?
Can add KNO3 and KH2PO4 for plants, and not need K2SO4.
I prefer to add a little of everything:hihilet the plants sort it out)
If I wanted to reduce the need for trimming plant's as has been mentioned by OP,I would simply reduce light energy and temperature before practicing nutrient limitation.


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## dukydaf (Dec 27, 2004)

Teebo said:


> My ratio thoughts have nothing to do with toxicity at all, I have already stated my reasoning and it was answered here: "15-20ppm NO3 might mean just as well you have ~0ppm K in plant available form."
> 
> I will continue adding Potassium to my tanks that have higher levels of Nitrate. The reason I did not mind low nitrate levels is because in an established tank it keeps trimming maintenance low, why dose just to trim if its filled out the way you want it? Long as it stays green the way it was I was happy.


Glad I could be of help.You are right the approaches we use largely depends on the plant selection and goals. You might however try what roadmaster suggested ( light limitation). Another option is to practice phosphate limitation as it seems less hard on plants. In freshwater "natural" bodies phosphate limitation is often the case, not nitrate limitation.



rhiro said:


> I have never seen this statement anywhere in all the planted tank/aquascaping literature I have read. Could you advise where you got this information?


Sure. The conc. of NO3 is linked to the conc. of K only if you add KNO3, as EI suggests (or other solutions that have both NO3 and K). If you dose according to EI, this is a non-issue.

Many fish-only aquariums have high NO3, but I doubt K conc. would be significant. Why is this ? NO3 can originate from other sources...urea, amino acids (nitrification cycle is the search term if you want to read more). These sources are present in planted aquariums as well. You can for example use urea as your only source of N and never add KNO3 to the aquarium. Thus it follows that there is no obligate correlation between the levels of K and NO3. This post goes into even greater detail https://www.intuitiveaqua.net/care/dosing-one-parameter/


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## rhiro (Sep 21, 2012)

dukydaf said:


> Sure. The conc. of NO3 is linked to the conc. of K only if you add KNO3, as EI suggests (or other solutions that have both NO3 and K). If you dose according to EI, this is a non-issue.
> 
> Many fish-only aquariums have high NO3, but I doubt K conc. would be significant. Why is this ? NO3 can originate from other sources...urea, amino acids (nitrification cycle is the search term if you want to read more). These sources are present in planted aquariums as well. You can for example use urea as your only source of N and never add KNO3 to the aquarium. Thus it follows that there is no obligate correlation between the levels of K and NO3. This post goes into even greater detail https://www.intuitiveaqua.net/care/dosing-one-parameter/


Sorry, I misunderstood the context of the statement that Teebo used. After re-reading all the posts I realize my mistake. I fully understand the nitrification cycle and the possible different sources of nutrients. I use NO3 as the controlling nutrient for plant growth with the goal of keeping it low to maintain slow/moderate plant growth.


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## Surf (Jun 13, 2017)

> K is not typically a problematic nutrient. I have had 20,30,40,60,80 and 100+ K ppm levels in my tanks with no issues.


While he didn't notice ant issues, that doesn't mean the fish were not affected. excess levels of anything can have health impacts that may effect the quality of life for the fish without killing it. it might weaken the fish immune systems and damage internal orgins. Furthermore the primary reason for large water changes in an EI tank are to excess nutrient (potassium, sulfur, chloride, and many others) from building to dangerous levels (whatever those levels are. However if we could balance the supply of nutrients in the fertilizer to the plants needs much of this excess could be avoided perhaps fewer or smaller water changes would be needed and the fish might be healthier. 

I agree with trying to balance nutrients with plant uptake but there are issues that are hard to resolve: 

1. Not all plants consume nutrients at the same level. For example C4 plants need more sodium than the more common C3 plants. Some plants need more sulfur while others need less. There is no one magic ratio of nitrogen to potassium.

2. Depending on the plant and fish load and amount of food consumed will very from tank to tank meaning the nutrient needs of each tank could be different.

3. Tape water series in its composition. Some tap water may have high potassium levels but low nitrogen content. With fertilizer we add nitrogen to correct for that but in the process we push the potassium content even higher. 

4. Most people don't know what there potassium and sulfate levels are or what the levels are for the micronutrients are. Potassium and sulfate test kits are hard to find. test kits for micronutrients are generally not available or very hard to find in most stores.

With all those unknown the best way to know what the ratio for your tank is. assuming you can find a test kit. the best solution Is to monitor the nutrient uptake by the plants and adjust the dosing level to try and compensate. However doing this can have unwanted side effects. If you decide to reduce potassium by reducing potassium phosphate dosage you could trigger hard green spot algae on the glass. Hard Green spot algae loves water low in phosphate. This can be addressed by scrapping it off the glass (more maintenance) or by increasing phosphate levels or by switching to a different phosphate fertilizer that doesn't contain potassium. 

One could use calcium phosphate which unfortunately increase calcium levels and water hardness. Or one could drop potassium nitrate and try to replace the nitrogen with urea, ammonia nitrate, or calcium nitrate. Each of these has some limitations. Urea can breakdown into ammonia (which is toxic) Ammonia nitrate is also a explosive ingredient and may not be available in some places due to legal restrictions. Calcium nitrate again will increase GH.

There are limits to what we can do. It is probably very difficult to reduce potassium levels as much as you want.


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