# Dosing Calcium Chloride and Magnesium Sulfate



## jayrug (Oct 22, 2004)

I bought both the Calcium Chloride and Magnesium Sulfate off Greg.

Hoping someone can help this poor math challenged fellah.
I know it's a 4:1 ratio, but I can't find how to dose to raise the GH.

How much would I dose of both to raise the GH 1 degree in a 55 gallon tank?


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## ThomE (Aug 26, 2004)

Damn Jayrug,

That's a hard question. But I think I can help ya out a little ..



> about one gram of mixed calcium chloride and magnesium sulfate (mixed 6:7 by weight) will raise 10 gallons of water by 1 degree general hardness (1 dGH) and provide an ideal calcium to magnesium ratio (3:1)
> 
> by Kevin Zippel, Ph.D


So, you need 2.54 grams of CaCL2 & 2.96 grams of MgSO4 to raise 55 gallons 1dgh.

I use 3:1 for my tank and it hasn't cause any issues.

Good Luck


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## jayrug (Oct 22, 2004)

Wow thanks ThomE I didn't realize it would be so precise like that. I figured it would be something like 1tsp CaCL2 1/4tsp MgSO4..

Time to break out the jewelers scale


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## Sven (Dec 3, 2002)

Sorry for reviving this old thread but how often are you dosing the calcium chloride now? 
I´m not to sure on the dosing of the CaCl, do you dose just once a week after WC? or every other day? Any tips would be much apreciated, I also have a 55g.


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## jayrug (Oct 22, 2004)

I just dose once a week after WC. 

The GH doesn't budge until i change the water.


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## Betowess (Dec 9, 2004)

ThomE said:


> Damn Jayrug,
> 
> That's a hard question. But I think I can help ya out a little ..
> 
> ...


So to get approximately 5dGH on a 50 gallon water change, would I need about 12.7 grams of CaCL2 and just under 15 grams of MgSO4? My tap GH is darn near zero.

I think I'm noticing a calcium deficiency and I am leaning toward ditching the oyster shells and trying to get more precise. I use epsom for Mg. And would you mix a batch of the two and then teaspoon it out into a water change prep tank. Because I have to use a prep tank to raise my soft pH to off gas CO2 - I have very soft well water which is in the low 5 pH out of the well's tap. By off gassing for a day or so I can get my pH up a little over a degree.But I'm still left with zip GH and KH. I usually add a little baking soda to bring up the KH too. Any help much roud: appreciated. bob


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## Hypancistrus (Oct 28, 2004)

That's WAY WAY too much magnesium. Most people either do a ratio of 3:1 calcium:magnesium or 4:1 calcium:magnesium.

The numbers for a 4:1 ratio are:

For 1 dGH per gallon - 0.07939 grams CaCl2*2H2O, and 0.03327 grams MgSO4*7H2O (epsom salt).

So, to raise 50 gallons by 5 dGH, you want *19.85 grams of CaCl2**2H2O and *8.32 grams of MgSO4**7H2O.


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## ThomE (Aug 26, 2004)

*Note: this is from my experience and research on the web. 


HHmmm, this is a pretty tough question to really hit with the right answer.

I use a 3:1 ration, but I use RO/DI water. I also add seachem so that might help too.

But If I was going to raise 50 gallons 5 GH, I would add 11.54 CaCL2 and 13.46 Mg.

Now, this is the funny part

A) There are different types of CaCL2, so depending on what you add the results may vary. :icon_roll 

B) You could actually add too much CaCL2 or Mg, so I would get a calcium test kit and test them. When you know what your Ca & GH is, you can back in to what your Mg levels. (I'm a geek, so I like testing to give me a better feel for the tank) Just because your PH is 5 when it comes out, this could mean you have a crazy amount of GH, but no KH.  . Too make matters worse, if you have too much CaCL2 or Mg, this also cause Iron uptake issues. :icon_conf . I figured since I add K, NO3, and P all separately, I also have a solution of Ca and another bottle of Mg. But I really only test my GH once every three weeks when I do water changes. Quick note: I tore out all my quick growing plants and now my tank consist of slower growing plants. This allows me to do water changes once every 3 weeks (I've only had this set up for 2-3 mths, so it's still in the 'test' phase)

C) The good news is this is a fish tank, not rocket science. Don't worry about getting exact measurement. The tank will accept a nice margin of error too. 

Hope this helps :icon_bigg


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## Betowess (Dec 9, 2004)

Thanks Thom, and Thanks Hypancistrus,

My Calcium Chloride is the stuff Gregg Watson sells. My well water is fairly near zero GH and KH according to AP tests. Not sure wether to do 4:1 or 3:1 ratio.  Maybe I'll split the difference. I see some white residue on the top of the change tank, so there is probably some calcium in the water, just not much. But like you said, there is a margin for error. And my tanks always experience some large margins of error thanks to me, from time to time.

Any recomendations on preferred calcium tests? Thanks again. bob


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## dataguru (May 19, 2004)

Found this old thread via a google search, so I thought I'd resurrect it since I'm working on a calculator for reconstituting RO water.

Can anyone double check my calculations?
I've double checked the dose and resulting ppm of ca, mg, and K on APC's fertilator. 

However, my doses don't match the shortcut from this thread 


> The numbers for a 4:1 ratio are:
> For 1 dGH per gallon - 0.07939 grams CaCl2*2H2O, and 0.03327 grams MgSO4*7H2O (epsom salt).


My spreadsheet is here:
http://thegab.org/Betty/Calc.xls


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