# Which kind of potassium should I use?



## lakshen99 (22 May 2021)

Im gonna be making my own macro mix with one of 3 types of potassium. 
1: Potassium chloride in the form of muriate of potash. NPK 0-0-60
2: Food grade potassium chloride
3: Potassium sulphate. NPK 0-0-51 + 18S 
which is the best that I should use together with Monopotassium phosphate and potassium nitrate?


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## Zeus. (22 May 2021)

Doesn't really matter. I have used 100% K2SO4 in the past to make my target [K] without any issues.
Some do blend the KCl and K2SO4 used to keep the the [SO4] levels lower


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## lakshen99 (22 May 2021)

Actually I found out from asking another forum that the iron impurities in muriate of potash (the reason why the powder is reddish) would react with phosphate at ph > 7 forming an insoluble precipitate. I posted on here before about my problems of my premixed macro turning cloudy when mixed with RO water. A quick google shows that RO water is ph7. When I mixed it with regular tap water, it doesnt turn cloudy.


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## lakshen99 (22 May 2021)

Since this occurs, will it be an issue if I make separate solutions of potash and phosphate and dose it into the aquarium at the same time.


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## dw1305 (22 May 2021)

Hi all,


lakshen99 said:


> will it be an issue if I make separate solutions of potash and phosphate and dose it into the aquarium at the same time.


No, that should be fine. The dilution effect should mean that the PO4--- remains in solution. Iron (Fe) may be more of an issue, dependent upon the pH of the tank water.


lakshen99 said:


> the iron impurities in muriate of potash (the reason why the powder is reddish) would react with phosphate at ph > 7 forming an insoluble precipitate


If it is a mined supply it is <"likely to contain iron (Fe)">.


lakshen99 said:


> A quick google shows that RO water is ph7


Google is wrong, theoretically it should be pH7, but it won't be. There are two reasons, pH isn't a very useful measurement in <"very soft water">, and atmospheric <"CO2 will diffuse into the water"> , lowering the pH to ~pH6.


lakshen99 said:


> which is the best that I should use together with Monopotassium phosphate and potassium nitrate?


You don't actually need to use any of them, can just use those two. They both supply a useful anion (PO4---, NO3-), as well as the K+ cation. If you do want to add more potassium, on its own, using the food grade potassium chloride (KCl) is probably best.


lakshen99 said:


> Potassium chloride in the form of muriate of potash. NPK 0-0-60


Last one is a bit of a strange one,  the "60" value isn't as a percentage, it is the potassium (K) value expressed as <"potassium oxide (K2O)">, meaning you need to multiply by 0.83 to get the potassium content.

cheers Darrel


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## lakshen99 (23 May 2021)

dw1305 said:


> Iron (Fe) may be more of an issue, dependent upon the pH of the tank water.


the issue being that iron would bond with phosphate?
If I decide to use potassium sulfate instead, what would the maximum sulfate levels in the aquarium without affecting fish, shrimp, and plants?
Also would sulfate react with any other nutrients in the tank?


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## dw1305 (23 May 2021)

Hi all, 


lakshen99 said:


> the issue being that iron would bond with phosphate?


<"Yes it is">.


lakshen99 said:


> what would the maximum sulfate levels in the aquarium without affecting fish, shrimp, and plants?


I don't know, <"quite high (several hundred ppm?)"> would be my guess, but it would be a guess. Hard water is also likely to be fairly sulphate rich naturally. 


lakshen99 said:


> Also would sulfate react with any other nutrients in the tank?


Yes, it can do, it is only really calcium (Ca) that is likely to be an issue. Have a look at the <"solubility rules chart">.

cheers Darrel


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## three-fingers (23 May 2021)

I find my fast growing stem plants always show signs of potassium deficiency when I just dose my mix of KNO3 and KH2PO4, so I usually just add a teaspoon(ish) of soluble "Sulphate of Potash" to the bucket whenever adding new water to the tank. I usually add Epsom salt (magnesium sulphate) at the same time too.

I've even just chucked granular (meant for sprinkling anound your garden) into a breeding net (with plants growing out of it lol) and just let it slowly dissolve.

I, too, have been worried about sulphate/chloride accumulaton in the past, but have since reached the conclusion that this really isnt an issue as long as you do at least the occasional water change, I think it could only be an issue very long-term in a tank that only ever gets top-ups an no actual water changes .  I would still prefer sulphate to chloride salts for freshwater aquarium use, but use both fairly haphazardly nowadays with no issues or worries!


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## lakshen99 (24 May 2021)

dw1305 said:


> Hard water is also likely to be fairly sulphate rich naturally.


would the addition of sulfate into the water increase its hardness? if so by how much


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## dw1305 (24 May 2021)

Hi all, 


lakshen99 said:


> would the addition of sulfate into the water increase its hardness?


No increase hardness, it is just to do with the depositional basins that the limestone (that forms the aquifer) was laid down in.  You often get evaporite minerals (like <"Gypsum (CaSO4.2H2O)) and Epsom Salts (MgSO4.7H2O)"> present when limestone is forming. 

cheers Darrel


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## lakshen99 (25 May 2021)

I just bought some Kno3, kh2po4, and k2so4 and will start making my own. If I put the solution in clear plastic bottles, do I need to keep it away from light?


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## dw1305 (25 May 2021)

Hi all, 


lakshen99 said:


> do I need to keep it away from light?


No, it is only iron chelates, like FeEDTA, that need to be kept in the dark (they photodegrade in the light).   

cheers Darrel


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## lakshen99 (25 May 2021)

dw1305 said:


> Hi all,
> 
> No, it is only iron chelates, like FeEDTA, that need to be kept in the dark (they photodegrade in the light).
> 
> cheers Darrel


Thanks a lot Darrel!
Am gonna try making my own micronutrients using csm+b. What liquid do i mix with the powder? Distilled water or does it have to be some kind of acid?


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