# GH and dosing Magnesium Sulfate



## fraynes1 (May 2, 2005)

Do I need to add Epson salts if I have a GH of over 100? I am using eco-complete and expect it to drop in the not so distant future.

I'm kind of lost when it comes to the calcium and Magnesium Sulfate. Is the GH reading 1/2 calcium and 1/2 Magnesium Sulfate. And I take it that dosing Magnesium Sulfate will raise GH?

Thanks for helping me understand!!! :icon_redf :icon_redf


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## Spar (Aug 7, 2003)

GH of 5.5d+ ( > 100 ppm) is fine alone, but it may not hurt to dose extra Mg anyway. I have a GH of 7 in tap water and still dose 1/2t of MgSO4 in my 50g after each water change.

THe reading is more complicated than just 1/2 and 1/2 CA/Mg in your readings. I think the general reading is 4:1 Ca:Mg, or at least what people aim for. Unfortunantly without spending tons of money on expensive testkits you cant get a formal reading on the value of each of these. Even Ca testkits are better utilized in SW tanks rather than FW.


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## BSS (Sep 24, 2004)

When you state 100, I'm assuming you mean ppm, which would be a shade over 5 dKh. My tap water runs a shade over 10 dKh. I've not been able to come up with a useful local tap water report, so I assumed I was good on the Mg and Ca front. I've always had trouble growing A. reineckii, though many consider it one of the easiest red plants. A fellow Floridian recently suggested I start adding Mg (via Epson's Salts) because he learned that most of the GH in his Florida water wat Ca. Well, I've only been adding 1/4 tsp 3x a week for about two weeks, and I can already see the difference.

So, in short, maybe yes, maybe no!


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## plantbrain (Dec 15, 2003)

Won't hurt to add a tad once a week after a water change.

Regards, 
Tom Barr


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## Hypancistrus (Oct 28, 2004)

Most people dose calcium and magnesium in a 3:1 or 4:1 ca:mg ratio.

The numbers are as follows:

3:1 ca:mg ratio:
74.43 mg CaCl2*2H2O
41.59 mg MgSO4*7H2O
--> raises 1 gallon by 1 dGH

4:1 ca:mg ratio:
79.39 mg CaCl2*2H2O
33.28 mg MgSO4*7H2O
--> raises 1 gallon by 1 dGH

Example: to raise a 50 gallon tank by 4 dGH with a 4:1 ca:mg ratio, add 15.88 grams CaCl2 and 6.66 grams MgSO4.

Don't add only MgSO4, the greater part of GH should come from calcium.

Don't mix the CaCl2 and MgSO4 together, or the calcium will precipitate out (the Ca combines with the SO4 and forms calcium sulfate which is insoluble).

You may need to add a little more or less based on results from a test kit. You can, for example, mix the CaCl2 and MgSO4 in seperate 200 mL beakers and add say 120 mL of each to dose at 60% strength.

Note that this is against the ever popular "EI" method, which says to just estimate the amount and dump it in without testing.


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## Spar (Aug 7, 2003)

the actual ratio (i.e. 4:1) doesnt really have an effect though does it? isn't it just a general range of acceptible levels of each Ca and Mg?

He already has a ~5dGH reading, so is it necessary to still increase Ca along with Mg?


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## inthedeep2 (Apr 6, 2005)

sorry to piggy back thie thread but i have a dumb question. just woundering with the epsom salt do you mix it with water before adding it to the tank or put the crystals in to the tank? if you mix it how much water to salt?
thanks


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## cfide (May 27, 2005)

I have seen Magnesium Suplhate in drug stores but I do not remember seeing CaCl2. Where is it sold?


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## Spar (Aug 7, 2003)

it is always better to disolve first in water. you dont want to risk a fish taking in a mouth ful. it can also burn holes through leaves of plants of sitting on it.

water to salt does not matter. I just get a cup full of tank water and stir. if it is too concentrated then pour out some of the water that has already been stirred, refill with tank water and continue stirring. You wont be putting much anyway in the tank (1/2t at most maybe) so you shouldnt have to go to this extreme.


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## inthedeep2 (Apr 6, 2005)

SPAR- you say about 1/2t is that for what size of tank? i have a 29gl so i really dont believe id need that much maybe 1/4. also useing the fleet enema for KH2PO4 do you just drip some drops into the tank?


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## Spar (Aug 7, 2003)

the 1/2t is for 40g's of water (50g tank). 1/4t would be plenty for you.

ive never personally used the Fleet Enema. However, it is always better to dose outside of the tank. i.e. In a cup of water and then pour into tank. You dont want to risk getting too much in there accidentally.


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## Rex Grigg (Dec 10, 2002)

cfide said:


> I have seen Magnesium Suplhate in drug stores but I do not remember seeing CaCl2. Where is it sold?



Greg Watson sells it. Or you can get it at most home brew beer supply stores.


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## inthedeep2 (Apr 6, 2005)

Spar said:


> the 1/2t is for 40g's of water (50g tank). 1/4t would be plenty for you.
> 
> ive never personally used the Fleet Enema. However, it is always better to dose outside of the tank. i.e. In a cup of water and then pour into tank. You dont want to risk getting too much in there accidentally.


 once you mix in the cup out of the tank then do you test the cup of water or do it so you dont accidently put too much in the tank..


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## Rex Grigg (Dec 10, 2002)

Mainly so the fish don't try and eat it.


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## plantbrain (Dec 15, 2003)

Hypancistrus said:


> Note that this is against the ever popular "EI" method, which says to just estimate the amount and dump it in without testing.


No it's not.
Why do you say that?

You can test if you so chose, I'm saying you do not "have to" test.
There is a big difference between these two statements.

Testing, making solutions etc works just fine with EI and keeps things more consistent. Many do that.

I've explored a wide range of nutrient levels while maintaining the others in excess, this way I know what ranges I can get away with and still have good growth.

You can tweak a tank and individualize it easily with or without test kits.
Test kits are fine, provided they are correct, often times, they aren't.

Most GH kits are fine.

This person has a GH of 100ppm+
If they have 90% of this Mg, I'll be a monkey's uncle.
So adding MgSO4 will target any potential Mg issue.
This is common sense and knowing what most tap water's consit of.

CaSO4(Gypsum) is not easily to preciptate nor dissolve. Adding Ca++ to SO4
at high concentrations, say like that of seawater, does not cause these ions to preciptate now does it?

(7.7% of the total salt in seawater is SO4 and roughly 1.2% is Ca out of the 35000 ppm total) So about 420 ppm of Ca++ and ~2700ppm of SO4. 

In fresh water below pH 11 or so, calcium ions are essentially free. That is, they are not strongly attached to anything else except water and move about independently of all other ions in the solution (exceptions being if the water has certain calcium-complexing agents in it, such as phosphate or certain organics). 

A simpler method, mix MgSO4 with CaCl2 and see if you get a precipitate at all.

If you use solutions, and make them concentrated enough, you might be able to.

Still, in this specific case, this whole mess is hardly required.

All that needs done:
Add MgSO4 after the water change once a week at 1/4 teaspoon per 25 gal is far beyond any need by plants.

That would rule out any GH/Mg/Ca related issue.

If they still have issues, then we know it's something else.

Regards, 
Tom Barr


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## fraynes1 (May 2, 2005)

So, Plantbrain I take it dosing 3/4 of a teaspoon once right after a w/c in my 75 gal. would suffice for the whole week? I use Eco-Complete so my GH should eventually drop, at what degree hardness should I start dosing more regular and in what amounts?

Also, when I dose my dry ferts I have just been dumping it in the tank with no problems, is this a bad thing or should I be dissolving it first?

Thanks 
Wayne


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## Hypancistrus (Oct 28, 2004)

plantbrain said:


> A simpler method, mix MgSO4 with CaCl2 and see if you get a precipitate at all.


http://www.plantedtank.net/forums/showthread.php?t=17431


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## Betowess (Dec 9, 2004)

For my near zero GH well water, I dose 4:1 ratio 19.85 grams of calcium chloride (Greg Watson is the source) and 8.32 grams of Mg (Epsom Salts) for a 5dgh on 50 gallons of change water. Sometimes I dose a 3:1 ratio which is 11.54 grams of Ca chloride and 13.46 grams of Mg. These numbers were furnished to me by some of the chem gurus on our forum. Obviously, one could take a percentage out to modify for your tank's change water and size. And most don't have to add calcium like I do. bob


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