MgSO4 versus MgSO4.7H2O - Fertilizing - Aquatic Plant Central

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Old 04-05-2009, 08:04 PM   #1 (permalink)
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Default MgSO4 versus MgSO4.7H2O

How can I figure how much MgSO4 I would need. I looked at the Fertilator but it only lists MgSO4.7H2O. I know they aren't the same but could use some help figuring it out.

I know they have the Various CaCL2 listed (CaCL2, CaCL2.2H2O, CaCL2.6H2O) and each will give a different ppm for the same measurement.

I will be reconstituting RO water for my tank and am aming for 5 GH and 5 KH. I got hte Baking Soda figured out for the KH and the CaCL2 for the Ca part of my GH booster.

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Old 04-06-2009, 03:55 PM   #2 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

Making your own formula for reconstituting RO water is a very difficult problem. It is daunting for the PhD chemist.
That being said if you cannot figure out the difference in the amount of MgSO4.7H2O vs MgSO4 I tend to believe you are going to have a lot of trouble.
If you still want to try….use about 1/2 the amount of MgSO4
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Old 04-06-2009, 04:13 PM   #3 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

Quote:
Originally Posted by ray-the-pilot View Post
Making your own formula for reconstituting RO water is a very difficult problem. It is daunting for the PhD chemist.
That being said if you cannot figure out the difference in the amount of MgSO4.7H2O vs MgSO4 I tend to believe you are going to have a lot of trouble.
If you still want to try….use about 1/2 the amount of MgSO4
Making it isn't the hard part. I'm not looking for the differences in chemicals just the weight difference for my equation.

I understand the difference in compunds nowing that the MgSO4 is the Anhydrous source and the MgSO4.7H2O is Epsom Salts. Contains 51% water in the break down.

Since I'm not a chemist I figured someone might have the info I need to clarify my situation.

Only 2 things are needed to reconstitute RO want to adjust the GH:

Calcium- I'm using CaCL2
Magnesium- Ordered MgSO4 but have been told my others here what I will probably receive is MgSO4.7H2O from the place I ordered from.
Potassium Sulfate (optional item but is used in most readily availble GH Boosters and Equilibrium.) Not needed as I dose plenty of K as it is.


Definitely not a hard thing to do with a decent Gram Scale to make the measurements. A Triple Beam would be even more accurate or possibly a high end digital.

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Old 04-06-2009, 04:30 PM   #4 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

Well, I don’t know what formula you are using to reconstitute your RO water but CaCl2 has too much Cl- to work as a good candidate. Cl- is not recommended in high levels because it is toxic to some fish and plants. CaCl2 is not the way Calcium is present in normal water.

CaSO4 and MgSO4 are usually used but they have solubility problems.

Actually, if you post the formula you are using, I could tell you what problems you are likely to encounter when you use it.
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Old 04-06-2009, 05:10 PM   #5 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

Here is the link.

Diana Walstad is the one who has worked with this idea.

http://www.aquaticplantcentral.com/f...-increase.html

Using CaCL2 is useed to avoid an increase in PH I am trying to not have my PH change or as little as possible as upping my KH will cause a .7 increase in PH which is neglible.

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Old 04-06-2009, 05:13 PM   #6 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

For the formulas I've ben using various ones but have been playing with the Fertilator on this site. Mixing 1g of CaCL2 to 1g MgSO4.7H2O will give me a 3.66:1 ratio which is close enough for my needs. I will actually be mixing 5g ata time and using 4g CaCL2 and 4g MgSO4.7H2O to up my gh from 0.5 Ro water to 5.44 dGH or 97.16 ppm

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Old 04-10-2009, 04:28 PM   #7 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

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Originally Posted by CraigThor View Post
For the formulas I've ben using various ones but have been playing with the Fertilator on this site. Mixing 1g of CaCL2 to 1g MgSO4.7H2O will give me a 3.66:1 ratio which is close enough for my needs. I will actually be mixing 5g ata time and using 4g CaCL2 and 4g MgSO4.7H2O to up my gh from 0.5 Ro water to 5.44 dGH or 97.16 ppm

Craig
It is difficult to say what will happen with your water since you do not say what your tank size is but estimating from your GH changes I guess that your tank size is 15 gal.

If that is true you will increase the level of Cl- to 23 ppm which is OK but high. I target my Cl- below 5 PPM.
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Old 04-11-2009, 08:10 AM   #8 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

WOW!

Ray-the-pilot: Making your own formula for reconstituting RO water is a very difficult problem. It is daunting for the PhD chemist.

No, substituting one chemical for another is NOT A DIFFICULT PROBLEM. You do not need a PhD. As a matter of fact it is a fifth grade chemistry class (at least in my home country which is Russia).

If you know the chemical formula of the compound (MgSO4.7H2O for example), you first need to calculate its molecular weight. This means how many grams one mole of the compound weights. You need to sum up molecular weights of individual elements. Molecular weights for each individual element are listed in the Periodic table (see http://www.webelements.com or fifth grade chemistry book).

For MgSO4.7H2O (which consists of one molecule of MgSO4 and seven molecules of H2O) you should get 12(Mg)+16(S)+4*8(O4-four oxygen atoms) + 7*( 2*1(H2)+8(O))=130 g
For MgSO4 you will get 12(Mg)+16(S)+4*8(O4-four oxygen atoms)=60 g

This means that one ppm of MgSO4 weights less than one ppm of MgSO4*7H2O, so to extract the same concentration of MgSO4 from both compounds you need to take 60/130=0.46 gramm MgSO4 for each 1 gramm of MgSO4*7H2O.

You can convert your calcium amounts (CaCL2, CaCL2.2H2O, CaCL2.6H2O) depending on exact compound you have at hand using the same formula.

One usefull tip: Trying to mix different salts can sometimes be a problem. For example, if you mix dry MgSO4 and CaCl2 and then add water, you may end up with insoluble mess ( although I did not try these particular salts, this is true for many other salts). But if you make two separate solutions (MgSO4 and CaCl2) and then mix them together it is perfectly ok (more complex chemistry is involved here though).

I hope this helps.
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Old 04-11-2009, 04:30 PM   #9 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

Quote:
Originally Posted by Natalia View Post
WOW!

Ray-the-pilot: Making your own formula for reconstituting RO water is a very difficult problem. It is daunting for the PhD chemist.

No, substituting one chemical for another is NOT A DIFFICULT PROBLEM. You do not need a PhD. As a matter of fact it is a fifth grade chemistry class (at least in my home country which is Russia).

If you know the chemical formula of the compound (MgSO4.7H2O for example), you first need to calculate its molecular weight. This means how many grams one mole of the compound weights. You need to sum up molecular weights of individual elements. Molecular weights for each individual element are listed in the Periodic table (see http://www.webelements.com or fifth grade chemistry book).

For MgSO4.7H2O (which consists of one molecule of MgSO4 and seven molecules of H2O) you should get 12(Mg)+16(S)+4*8(O4-four oxygen atoms) + 7*( 2*1(H2)+8(O))=130 g
For MgSO4 you will get 12(Mg)+16(S)+4*8(O4-four oxygen atoms)=60 g

This means that one ppm of MgSO4 weights less than one ppm of MgSO4*7H2O, so to extract the same concentration of MgSO4 from both compounds you need to take 60/130=0.46 gramm MgSO4 for each 1 gramm of MgSO4*7H2O.

You can convert your calcium amounts (CaCL2, CaCL2.2H2O, CaCL2.6H2O) depending on exact compound you have at hand using the same formula.

One usefull tip: Trying to mix different salts can sometimes be a problem. For example, if you mix dry MgSO4 and CaCl2 and then add water, you may end up with insoluble mess ( although I did not try these particular salts, this is true for many other salts). But if you make two separate solutions (MgSO4 and CaCl2) and then mix them together it is perfectly ok (more complex chemistry is involved here though).

I hope this helps.
I am very much impressed!

I have three grandchildren in school here in the US. One is 11 years old and in the sixth grade and quite intelligent but I know he couldn’t tackle the problem the way you did. I am very much impressed!

I think you alluded to the problem yourself when you said that there is a lot more chemistry going on here. When I said that you needed a PhD degree in chemistry I didn’t mean to imply that you needed one to calculate formula weights and convert molarities of compounds. I meant that you have to know a lot of chemistry to prevent getting insoluble gunk in your water.

It is very easy to say I can make an RO water reconstitution but it is very hard to actually give a working formula. If you have one tell us about it. I for one am really interested in finding one!

BTW I for one have spent a lot of time calculating out those formulas like you did only to find I got gunk when I put the chemicals in my tank.
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Old 04-13-2009, 03:35 AM   #10 (permalink)
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Default Re: MgSO4 versus MgSO4.7H2O

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Originally Posted by ray-the-pilot View Post
It is difficult to say what will happen with your water since you do not say what your tank size is but estimating from your GH changes I guess that your tank size is 15 gal.

If that is true you will increase the level of Cl- to 23 ppm which is OK but high. I target my Cl- below 5 PPM.
I'm only reconstituting 5g of RO water.

4g of CaCL2 and 4g of MGSO4.7H2O will adjust the GH by 5.44ppm

1g of CaCL2 = 19.08 ppm or 1.07 gh
1g of MgSO4.7H2O = 5.21 ppm or .29 gh

1.07/ .29 = 3.66:1 ratio of Ca to Mg. The ideal ratio is 4:1 so this is close enough for me.

In order to get my gh up to ~5 I need to use 4g of each CaCL2 and MgSO4.7H2O. This keep along with the 3.66:1 ratio. I will actually end up with 97.16 ppm or 5.44 gh.

I will also add a bit of Baking Soda to give a slight increase in the KH as well.

The difference in 1g of CaCL2 and CaCO3 in 5g of RO water is the following:

1 gram CaCL2 in 5 gallons RO water = 19.08 ppm or 1.07 gh change
1 gram CaCO3 in 5 gallons RO water = 21.15 ppm or 1.18 gh change.

I currently have 2 lbs of CaCL2 and will give it a try. I've also read the CaCO3 will raise hte PH of the water where as the CaCL2 won't have the same impact on the tanks water.

LMK if I can provide you any other information.

Craig
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