# Magnesium's Contribution to General Hardness



## cS (Jan 27, 2004)

I don't have a GH test kit around, so would someone please inform me how much MgSO4.7H20 (Epsom salt) is required to raise GH by X degrees in Y liters of water?

Thank you.


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## Jay Reeves (Jan 26, 2004)

Check this out
http://www.csd.net/~cgadd/aqua/articles.htm
A online version is available and/or you can download a verison for windows. It is the first two "articles" listed on the page.

HTH,
Jay Reeves


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## cS (Jan 27, 2004)

Thank you for the information Jay, but I am actually looking for how much of an increase in GH would X amount of MgSO4.7H2O have on Y volume of water.

I've done the math and wonder if someone could test it out. Add 1 teaspoon MgSO4.7H2O (~5.4 gram) to 10 gallon (~38 liter) of water and see if the GH will increase by 3 degrees. Scale down/up if you don't have a spare 10 gallon tank around. 

Much appreciated.


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## Anthon (Feb 26, 2004)

1°GH of Mg = 4,35 ppm of Mg (be careful not 4,35 mg/L of MgSO4)


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## Steve Pituch (Jan 25, 2004)

Let's see.....

Isn't one german degree = 17.9 ppm? 17.9 ppm= 17.9 mg/liter. For gallons you would need 17.9 x 3.77 = 67.5 milligrams of Mg to raise one gallon 1 deg GH. Epsom salts are 9.9% Mg. So you would need 67.5/.099 = 681 mg of Epsom salts to raise 1 gallon of water 1 deg GH. Thats .7 gram Epsom salts to raise 1 gallon 1 deg GH.

Sounds like a lot! Can anyone check this?

Steve Pituch


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## cS (Jan 27, 2004)

Steve, you forgot to convert ppm CaCO3 to ppm Mg++.

1 german degree = 17.9 ppm CaCO3
17.9 ppm CaCO3 x .24 = 4.296 ppm Mg++ = 4.296 mg/liter Mg++
4.296 mg/liter Mg++ x 3.78 liter/gallon = 16.24 mg/gallon Mg++
16.24 mg/gallon Mg++ (246.476 mg Epsom salt / 24.305 mg Mg++) = 164.913 mg/gallon Epsom salt

That's .2 gram of Epsom salt to raise 1 gallon by 1 degree GH.

---

1 teaspoon Epsom salt = ~5.4 gram Epsom salt


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## Steve Pituch (Jan 25, 2004)

CS,

OK, thanks for the correction. My little instruction booklet that came with the AP test kit says that GH is a measure of the total Mg++, and Ca++ positive ions in the water. So I was just including the ions, not the entire CaCO3 as the basis of the measurement. I guess I was taking the instructions too literally.

Thanks,
Steve


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