Making Stock Solutions of CaCl2 and MgSO4 - The Planted Tank Forum
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post #1 of 22 (permalink) Old 10-02-2014, 01:46 PM Thread Starter
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Making Stock Solutions of CaCl2 and MgSO4

I've read lots of stuff regarding how much to dose a given amount of water with these elements; however, I am coming up short on how much to use to make a stock solution of each. I'd appreciate it if someone could assist.

The MgSO4 is strait MgSO4 and the CaCL2 is straight CaCl2.
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post #2 of 22 (permalink) Old 10-02-2014, 02:59 PM
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I have tried making a liquid GH booster in the past and I have had no luck what so ever. I have tried many different forms of mg and ca and nothing worked. I wish I could help but I cant. It would be interesting to see if anyone else has been successful though. In the end I just found it easier to use the dry version.
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post #3 of 22 (permalink) Old 10-02-2014, 03:28 PM
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I've never tried this but it should mix fine. Add the amounts below to 500ml of water. Dose 5ml per 10 gallons to yield the numbers below.

CaCl2.2H2O 185.37 gm (approximately 51 1/2 teaspoons)
MgSO4.7H2O 171.398 gm (approximately 33 1/2 teaspoons)


Ca 13.35
Mg 4.47
dGH 1
Cl 23.62
S 5.89
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post #4 of 22 (permalink) Old 10-02-2014, 04:41 PM
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I think the issue coule be the fert did not dissolve or some kind of reaction happened. I dose these ferts dry too but it would be nice to know if you can make it into a liquid solution.

I'm guessing it is too much for the amount of liquid we are talking about. Putting even 1/2 a dose for a couple of doses could be too much for say a 500 ml solution.


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post #5 of 22 (permalink) Old 10-02-2014, 04:56 PM
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It should dissolve. The maximum solubility of each is below per this solubility table. I'm not sure if a reaction could occur. If I had some CaCl2 I'd try it but I don't.

Solubility of CaCl2 is 372.5 grams in 500ml
Solubility of MgSO4 is 175.5 grams in 500ml
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post #6 of 22 (permalink) Old 10-02-2014, 06:49 PM Thread Starter
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Quote:
Originally Posted by Zorfox View Post
I've never tried this but it should mix fine. Add the amounts below to 500ml of water. Dose 5ml per 10 gallons to yield the numbers below.

CaCl2.2H2O 185.37 gm (approximately 51 1/2 teaspoons)
MgSO4.7H2O 171.398 gm (approximately 33 1/2 teaspoons)


Ca 13.35
Mg 4.47
dGH 1
Cl 23.62
S 5.89
That much? That many tsps in 2 cups of water? Forgive me for questioning something I am asking for help with. That seems like overkill.

For KNO3, by mixing 1 tbsp in 1 cup of water, 1ml of the solution will raise Nitrate to 2.16ppm in 5 gallons of water. That's what is raising question marks in my mind about the stock solution for the other two.

Did you mean 500l?
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post #7 of 22 (permalink) Old 10-02-2014, 07:00 PM
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Smile Not Part of the Solution? You Are a Precipitate!

Hi,

I wonder could there be some issue of ionic bonding…

Big 7, little 2?

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post #8 of 22 (permalink) Old 10-02-2014, 08:23 PM
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Hi,

Sorry I had to run, last post, sort of a drive by post, I apologize.

The relevant solubility is for CaSO4, about 1.2-grams in 500-ml and MgCl about 270-grams at 20C (68F).

This maybe one of the reasons Magnesium gets treated as a micronutrient.

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post #9 of 22 (permalink) Old 10-02-2014, 08:23 PM
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Quote:
Originally Posted by rpadgett37 View Post
That much? That many tsps in 2 cups of water? Forgive me for questioning something I am asking for help with. That seems like overkill.

For KNO3, by mixing 1 tbsp in 1 cup of water, 1ml of the solution will raise Nitrate to 2.16ppm in 5 gallons of water. That's what is raising question marks in my mind about the stock solution for the other two.

Did you mean 500l?
I just double checked those calculations here. Yes, they appear to be accurate. I simply made it as concentrated as it could be based on solubility. You can certainly increase the dose size.

However, like I said, I have no idea if there could there be a reaction. It sounds like Joe may know.
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post #10 of 22 (permalink) Old 10-02-2014, 08:50 PM
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Smile Sorry for Stepping on Your Post Zorfox

Hi,

Without worrying too much about the details, due to the polarity of water, strength will do, the ionic bond, the strength of their connection is overcome, the whole big 7, little 2, thing.

So for a little bit you have Ca++, Mg++ (cations) and Cl- (2 per CaCl2), SO4--(anions).

Due to ionic strengths after a bit (real quick in human time scales) the Ca++ and the SO4--find each other and form a strong double bond and will precipitate.

We can write this as:
CaCL2(aq) +MgSO4(aq) ---> CaSO4(s) + MgCl2(aq), in real life we only concern ourselves with the precipitate ions.

This is one of those reactions where many a religious leader insist that is you just heat the water and it will mix “more easily” (sic).

If you are not a true believer I can tell you the more you raise the temperature, the greater the rate of precipitation.

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post #11 of 22 (permalink) Old 10-02-2014, 09:08 PM
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Would adding CaCl2 to water, waiting for about 30 minutes or longer while agitating the water, then adding MgSO4 result in a CaSO4 precipitate?

Just wondering since I remineralize water for my shrimp in a 5 gallon bucket using CaCl2 and MgSO4 and I've only seen a precipitate form when they were added to the water at the same time.

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post #12 of 22 (permalink) Old 10-02-2014, 09:41 PM
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The timing shouldn't matter. Temperature definitely does. Warmer water will dissolve things better, even after it cools things are more likely to stay in solution. That's how you can super-concentrate things to grow crystals and stuff. Also using preparations with different conjugate ions helps. Like not using sodium bicarbonate with calcium bicarbonate. Because the bicarbonate will reach saturation and you wont be able to get the sodium or calcium into solution. I hope that makes sense. I know that doesn't directly apply here, but just for future reference.
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post #13 of 22 (permalink) Old 10-03-2014, 04:58 PM Thread Starter
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I'm doing my best, but the chemistry and such is over my head. Just the same, would it be better making the stock solutions of these two things separately? Would I need to be concerned about the chemistry if I were to prepare them this way? Or is the chemistry even a concern at all if I am only wanting to raise the GH of RO water to 7-8 dGH with a ratio of 1 Mg to 4 Ca?
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post #14 of 22 (permalink) Old 10-03-2014, 10:36 PM
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Hi,

Do not worry about the chemistry; as a practical matter certain combinations cannot be mixed together.

It does not matter how long you wait, whether you heat it or not.

Simply stated you cannot mix Calcium chloride and Epsom salt together in concentrations meant for dosing.

As a practical matter to raise the GH (general hardness) of RO (reverse osmosis) water in a large container mix the Epsom salts, thoroughly, then add the Calcium chloride a little at a time mixing as you go.

Do you mind sharing how much RO water, Epsom salt, Calcium chloride (do you know the hydrate?) you are adding, and what level of GH you are trying to reach.

Respectfully,
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post #15 of 22 (permalink) Old 10-03-2014, 10:53 PM Thread Starter
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Good to know, and no I don't mind sharing.

I bought the CaCl2 (No hydration listed) and MgSO4 from this vendor: http://www.aquariumfertilizer.com/in...tion1=products

I will be mixing these in 5 gallons of RO water for my small tanks. I haven't tried to mix anything yet to be sure I knew what I was doing. And the GH I hope to achieve is by adding 2GH of the MgSO4, then CaCl2 until the GH reaches 7-8 (closer to 8).

I've been sifting through a thread in a different forum started by Diane Walstad regarding using these items. The measurements provided are for adding them directly to the tank. I would prefer a stock solution as after I see how much is being used over a period of time, I can easily control the amount I add to ensure I stay at these GH values.
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