# MgSO4 versus MgSO4.7H2O



## CraigThor

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.

Craig


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## ray-the-pilot

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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## CraigThor

ray-the-pilot said:


> 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&#8230;.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.

Craig


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## ray-the-pilot

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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## CraigThor

Here is the link.

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

http://www.aquaticplantcentral.com/...-wet-thumb-forum-calcium-dosing-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.

Craig


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## CraigThor

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


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## ray-the-pilot

CraigThor said:


> 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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## Natalia

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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## ray-the-pilot

Natalia said:


> 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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## CraigThor

ray-the-pilot said:


> 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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## ray-the-pilot

CraigThor said:


> 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


Why you need a PhD in chemistry to do this!

Your estimates of GH are wrong. You are calculating the ppm of Ca+2 and Mg+2. You need to convert these values into equivalents of CaCO3. If you add 4 g of CaCl2 and 4 g MgSO4.7H2O to 5 gal of RO water the GH will be about 276 ppm or 15.5deg.

I hope you haven't tried this already!


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## CraigThor

ray-the-pilot said:


> Why you need a PhD in chemistry to do this!
> 
> Your estimates of GH are wrong. You are calculating the ppm of Ca+2 and Mg+2. You need to convert these values into equivalents of CaCO3. If you add 4 g of CaCl2 and 4 g MgSO4.7H2O to 5 gal of RO water the GH will be about 276 ppm or 15.5deg.
> 
> I hope you haven't tried this already!


How are the estimates wrong? I would like to see your math behind it for my info. I've also been posting in the thread I linked to earlier and Diana responded about hte Chloride issue and at what point it would be a problem.

Also if all the estiamtes are wrong you should contact this site as all the equations in the Fertilator would be wrong as well. The number for ppm of the MgSO4.7H2o and the CaCL2 I posted were from this sites Fertilator. I will go and link them here.

Craig


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## ray-the-pilot

The tool that you are using is correctly giving you ppm of Ca+2 and ppm Mg+2. This not the ppm GH. GH is measured in equivalents of CaCO3. To convert ppm Ca+2 to GH multiply the ppm by 2.5.
To convert ppm Mg to GH multiply the ppm by 4.1. 
When you add these up you will get the total GH in ppm of CaCO3. Divide by 17.8 to get the deg. GH


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## Natalia

_Ray-the -pilot_, my calculations agree with yours.

The confusion here comes because unlike in chemistry where we use molarities as a standard measure of concentration, in aquarium business there are degrees, ppms, etc.

Here is what I found:

GH(ppm)=2.5Ca+(ppm)+4.1Mg+(ppm) where ppm stands for part per million or milligramms per liter (mg/l)
to convert GH(ppm) in degrees divide by 17.86.

So, let's see what we get:

1g CaCl2/5gal=0.37g Ca+/(5*3.78)=19.57 mg/l or 19.57 ppm Ca+ ( I divided by 3.78 to convert gallons into liters)
Using GH formula, GH(ppm)=19.57*2.5=48.9ppm or 2.73 degree

1g MgSo4*7H2O/5gal=0.092g Mg+/(5*3.78)=4.88 ppm Mg+
Using GH formula, GH(ppm)=4.88*4.1=20.ppm or 1.12 degree

If we add 4g of each to 5gal of H2O the GH will be 15.4 degree.

I did not mean to hurt any feelings in my first reply. With or without a PhD it would be better to understand what we are dumping in our tanks and why. Otherwise the fish will float belly-up.

Also, a general rule is that if you dissolve your chemicals separately in water and then mix together you are less likely to end up with an insoluble mess.


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## Natalia

_Ray-the -pilot_, my calculations agree with yours.

The confusion here comes because unlike in chemistry where we use molarities as a standard measure of concentration, in aquarium business there are degrees, ppms, etc.

Here is what I found:

GH(ppm)=2.5Ca+(ppm)+4.1Mg+(ppm) where ppm stands for part per million or milligramms per liter (mg/l)
to convert GH(ppm) in degrees divide by 17.86.

So, let's see what we get:

1g CaCl2/5gal=0.37g Ca+/(5*3.78)=19.57 mg/l or 19.57 ppm Ca+ ( I divided by 3.78 to convert gallons into liters)
Using GH formula, GH(ppm)=19.57*2.5=48.9ppm or 2.73 degree

1g MgSo4*7H2O/5gal=0.092g Mg+/(5*3.78)=4.88 ppm Mg+
Using GH formula, GH(ppm)=4.88*4.1=20.ppm or 1.12 degree

If we add 4g of each to 5gal of H2O the GH will be 15.4 degree.

I did not mean to hurt any feelings in my first reply. With or without a PhD it would be better to understand what we are dumping in our tanks and why. Otherwise the fish will float belly-up.

Also, a general rule is that if you dissolve your chemicals separately in water and then mix together you are less likely to end up with an insoluble mess.


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## CraigThor

Natalia said:


> _Ray-the -pilot_, my calculations agree with yours.
> 
> The confusion here comes because unlike in chemistry where we use molarities as a standard measure of concentration, in aquarium business there are degrees, ppms, etc.
> 
> Here is what I found:
> 
> GH(ppm)=2.5Ca+(ppm)+4.1Mg+(ppm) where ppm stands for part per million or milligramms per liter (mg/l)
> to convert GH(ppm) in degrees divide by 17.86.
> 
> So, let's see what we get:
> 
> 1g CaCl2/5gal=0.37g Ca+/(5*3.78)=19.57 mg/l or 19.57 ppm Ca+ ( I divided by 3.78 to convert gallons into liters)
> Using GH formula, GH(ppm)=19.57*2.5=48.9ppm or 2.73 degree
> 
> 1g MgSo4*7H2O/5gal=0.092g Mg+/(5*3.78)=4.88 ppm Mg+
> Using GH formula, GH(ppm)=4.88*4.1=20.ppm or 1.12 degree
> 
> If we add 4g of each to 5gal of H2O the GH will be 15.4 degree.
> 
> I did not mean to hurt any feelings in my first reply. With or without a PhD it would be better to understand what we are dumping in our tanks and why. Otherwise the fish will float belly-up.
> 
> Also, a general rule is that if you dissolve your chemicals separately in water and then mix together you are less likely to end up with an insoluble mess.


This makes sense and also the equations listed make it much easier to understand. I had been googling for some equations but was coming up empty handed. Thanks for the clarifications from both of you.

Craig


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## ray-the-pilot

While Natalia and I may know some chemistry never trust anything without testing it first!

Make up a small batch of your reconstituted water and test the GH. That way you will have two confirming recommendations, one from me and Natalia and one from yourself.

BTW: While this formula for reconstituting RO water gets you to a good level of Ca+2 and Mg+2, it is very poorly buffered. The pH will change very rapidly and it will be hard to dissolve CO2 in your water. You really need to consider KH or carbonate hardness in your calculation. Normal water has KH = GH.


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## CraigThor

ray-the-pilot said:


> While Natalia and I may know some chemistry never trust anything without testing it first!
> 
> Make up a small batch of your reconstituted water and test the GH. That way you will have two confirming recommendations, one from me and Natalia and one from yourself.
> 
> BTW: While this formula for reconstituting RO water gets you to a good level of Ca+2 and Mg+2, it is very poorly buffered. The pH will change very rapidly and it will be hard to dissolve CO2 in your water. You really need to consider KH or carbonate hardness in your calculation. Normal water has KH = GH.


I'm buffering the KH with Baking Soda. I've already got that part down I just need help with this part. I will be shooting for a KH of 3-4 and a GH of 5-7. Now to get the scale out and dust off the test kits.

Craig


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## CraigThor

One last question.

How is the Ca from CaCO3 figured, I ordered some of that also. It won't be here till end of week but was curious.

Craig


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## Natalia

_CraigThor:_

As far as calcultions are concrned, the molecular weights of CaCO3 and CaCl2 are 50 and 54 respectively, so for each gramm of CaCl2 you should substitute 50/54=0.925 gramm of CaCO3, which is basically the same amount.

However, you will have a hard time trying to dissolve CaCO3, it is not soluble in water. Actually, salt deposits in marine tanks or eggshells are almost pure CaCO3. You need a strong acid to dissolve CaCO3 which is not a good solution when reconstituting RO water. In addition, CO3 will raise your KH, so you will need to adjust your baking soda accordingly.

I am wondering why you decided to go into this pain rather then just using commertial buffers for RO water (Discus buffer or Equillibrium) which contain all the necessary elements? Even if you get GH/KH right, there is a lot more that has to go in that water in order for the plants/critters to feel good, including minerals, trace elements and other stuff. The price of buying those separately would most likely be the same as buying a complete RO reconstitution buffer.

Also, in my tanks I would not use salts that are not aquarium of food-grade. These may contain other chemicals that could potentially be harmfull for plants/fish. I have seen posts on this forum where people dump strange things in their tanks and then wonder why all fish are dead next day.

My last question is what is you water source? If your water is hard but good quality you could just dilute it with your RO water untill GH/KH readings are in acceptable range. This is exactly what I do with my water.


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## CraigThor

Natalia said:


> _CraigThor:_
> 
> As far as calcultions are concrned, the molecular weights of CaCO3 and CaCl2 are 50 and 54 respectively, so for each gramm of CaCl2 you should substitute 50/54=0.925 gramm of CaCO3, which is basically the same amount.
> 
> However, you will have a hard time trying to dissolve CaCO3, it is not soluble in water. Actually, salt deposits in marine tanks or eggshells are almost pure CaCO3. You need a strong acid to dissolve CaCO3 which is not a good solution when reconstituting RO water. In addition, CO3 will raise your KH, so you will need to adjust your baking soda accordingly.
> 
> I am wondering why you decided to go into this pain rather then just using commertial buffers for RO water (Discus buffer or Equillibrium) which contain all the necessary elements? Even if you get GH/KH right, there is a lot more that has to go in that water in order for the plants/critters to feel good, including minerals, trace elements and other stuff. The price of buying those separately would most likely be the same as buying a complete RO reconstitution buffer.
> 
> Also, in my tanks I would not use salts that are not aquarium of food-grade. These may contain other chemicals that could potentially be harmfull for plants/fish. I have seen posts on this forum where people dump strange things in their tanks and then wonder why all fish are dead next day.
> 
> My last question is what is you water source? If your water is hard but good quality you could just dilute it with your RO water untill GH/KH readings are in acceptable range. This is exactly what I do with my water.


Reasonings' of using RO and reconstituting.

I dose plenty of K and have a nutrient rich substrate. Commercially available buffers contain ALOT of K which I don't need more of. I also dose plenty of Iron which is in several of the availble buffers as well. I dose traces daily into my tank along with Iron couple of times a week also.

Our water source is terrible. After our flood last year (22 ft over fllood stage and the city lsot 3 of the 4 wells and also the sewage treatment plant) the water is sketchy at best. My wifes cats and rabbits won't even drink the tap water. They have been extra heavy on the Chlorine/ Chloramines adn also lots of Ammonia in the water. Last year I lost $600 worth of fish in 1 water change and I had dosed my tanks with dechlorinator as usual. PH is 8.4-8.5 and the GH 7/ KH 5.

We buy RO water for ourselves to drink so the couple of extra gallons for the tank is nothign neither is add the couple of chemicals to make it what it needs to be. I'm just waiting on test kits to arrive to double check as they were out of stock locally.

Craig


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## CraigThor

Well just an update. 

4 days ago I dosed the following:

3/4 tsp MgSO4.7H2O
3/4 tsp CaCL2
1/2 tsp Baking Soda 

Into my tank. Tank pearls better than ever. Shrimp seem more active and the fish have better colors.

Yesterday I got my digital scale in the mail and today my test kits arrived.

Here is what the results were today:

PH: 6.6
GH: 9
KH: 5

I will be reconstituting some water tomorrow or monday and will do acurate weights and testing of the water before I do my water change.

This seems to be a good setting for the tank. Shrimp color is improved. Plants pearling more than ever. Ph is nice and stable not varying much at all.

Craig


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