# Gypsum and potash



## LAKA (Feb 11, 2007)

Is the fertilizer Sulphate of Potash OK for preparing in PPS pro. Is it pure K2SO4?
Gypsum for raising GH. Does it cloud the water? How long for? Where can i buy it?
LAKA


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## turbomkt (Mar 31, 2004)

Gypsum is readily available at your local Home Improvement store (Home Depot, Lowes, etc). It is used to help soften the ground for gardens, etc.


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## Salt (Apr 5, 2005)

"Potash" usually means it's an impure form.

Gypsum is also an impure form of calcium sulfate.


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## Laith (Sep 4, 2004)

Sulphate of Potash is K2SO4 so it should be fine for PPS-Pro.

Gypsum is calcium sulphate (CaSO4·2H2O). I've never used it but it's what's in chalk and another form of it is actually plaster of paris. Not sure how soluble this would be.

Also be aware that calcium sulphate will only add calcium to your water... GH is a measure of both calcium and magnesium (mostly) so if you want to raise GH it's best to add magnesium as well.


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## Salt (Apr 5, 2005)

It suprises me to no end how everyone still advises adding magnesium to raise GH when Edward posted proof years ago that too much magnesium (>10 ppm) causes stunting in some plants.


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## Edward (May 25, 2004)

LAKA said:


> Is the fertilizer Sulphate of Potash OK for preparing in PPS pro. Is it pure K2SO4? Gypsum for raising GH. Does it cloud the water? How long for? Where can i buy it?
> LAKA


Using a product because it contains certain chemical is irresponsible. How do we know Gypsum doesn't come mixed with latex, fungicide, etc? It may work for awhile and then you start wondering what is wrong here? Common names may also be misleading. 
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*If you don't see the right chemical formula on the product, don't use it.* 
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## Laith (Sep 4, 2004)

Salt said:


> It suprises me to no end how everyone still advises adding magnesium to raise GH when Edward posted proof years ago that too much magnesium (>10 ppm) causes stunting in some plants.


That may be true... but so is the fact that a deficiency of magnesium is also detrimental.  As far as I know, magnesium is a required macro nutrient for plants so some is necessary.

Keep in mind that there are tap waters where the GH is made up mainly of calcium with very little magnesium, even at higher levels of GH.

And Edward does have MgSO4 in the PPS-Pro mix... I assume that this is to ensure that there is no Mg deficiency.


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## Laith (Sep 4, 2004)

And Edward is right in his comments re knowing what else could be in there. 

My comments were based on the assumption that we were talking about "pure" Sulphate of Potash (K2SO4) and only CaSO4 with no other "contaminants"!


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## LAKA (Feb 11, 2007)

Laith said:


> And Edward is right in his comments re knowing what else could be in there.
> 
> My comments were based on the assumption that we were talking about "pure" Sulphate of Potash (K2SO4) and only CaSO4 with no other "contaminants"!


The Sulphate of Potash states on the bag about 50% K and 15% sulphate. Is this sufficient for PPS-Pro or do i need technical grade?

As for Mg. Water analysis of tap water shows i have 1ml/l of Mg so i supplement using fertilator with MgSO4 to desired levels.

I use CaCl2 for Ca but was looking at substituting with CaSO4 to reduce Cl in water.

I have 4mg/l of Ca in my tap water. I prefer to stick with CaCl2 if possible because i can only buy chemical in bulk from Australia ie. 25kg bags. for technical grade.
If i stick to CaCl2 to attain 20-30mg of Ca will this dose stunt my plant growth in terms of Cl. If it does i will then have to go to CaSO4.-more expense!
I've read about Cl and plants stunting but my understanding is this occurred in tanks with very high levels of the stuff.

LAKA


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