CaSO4 vs CaCl2

[MichaelJ]

If you want to reduce sulphate levels you can swap CaSO4 with CaCl2 (Calcium chloride). You will end up with a balanced mix of sulphates and chlorides rather than a higher amount of sulphates.

My case for using CaSO4 over CaCl2 is two fold: S is an essential macro and Cl is an essential micro/trace (which we usually get from our trace dosing), so by that I’d rather take the S. Secondly, for every 7.14 ppm of Ca I would get about 12.6 ppm of Cl. So unless you’re pre-batching and have to observe solubility, there is no compelling case for CaCl2 that I am aware of. Additionally, if you want to keep tds low and generally target low dGH my advice would be to go with CaSO4 - otherwise it probably won’t matter much as you can tell from the numerous successful tanks that use CaCl2 or CaSO4.

Cheers,
Michael

 

[Hanuman]

My case for using CaSO4 over CaCl2 is two fold: S is an essential macro and Cl is an essential micro/trace (which we usually get from our trace dosing), so by that I’d rather take the S. Secondly, for every 7.14 ppm of Ca I would get about 12.6 ppm of Cl. So unless you’re pre-batching and have to observe solubility, there is no compelling case for CaCl2 that I am aware of. Additionally, if you want to keep tds low and generally target low dGH my advice would be to go with CaSO4 - otherwise it probably won’t matter much as you can tell from the numerous successful tanks that use CaCl2.

Both S and Cl are used in very minimal amounts by plants so if one can reduce them there is no harm whether one is a macro and the other a micro. At levels added by even 1dGH that's already way more than enough, hence why reducing S is a no brainer for me, but it won't do harm if more as far as my experience goes.
CaCl2 is also more soluble in water.
CaCl2 also allows you to reduce your overall TDS, or let's be accurate here, your electrical conductivity. One could even add a pinch of CaCO3 to reduce Cl even further but in exchange you'll get some KH.
I personally don't have any Cl from my micro.

The choice between the two boils down to pure preference, really. I've been using CaSO4 for years, but moving away from it and now using CaCl2, to reduce EC.

 

[MichaelJ]

of CaCO3

Yes, In my soft water tank <2 dGH, I’m actually using CaSO4 -and CaCO3 to give me all my alkalinity (~0.5 KH) and that extra pinch of Ca to build dGH, works perfectly but you need to be down at about at a 6.2’ish pH to make the CaCO3 soluble in any meaningful amounts.

Cheers,
Michael

 

[MichaelJ]

The choice between the two boils down to pure preference, really. I've been using CaSO4 for years, but moving away from it and now using CaCl2, to reduce EC.

Hi @Hanuman, not sure how you came to the conclusion that CaCl2 would yield a lower EC/TDS compared to CaSO4 ? Your rarely off, so I ran a quick test just to make sure that I’m not off here either claiming CaSO4 also reduces your EC/TDS significantly (Im constantly on the hunt for reducing TDS so missing this would definitely make me go stand in a corner for 15 minutes ).

Targeting ~20 ppm of Ca in 1 US gallon (3.78L) of water:

Test 1:

Null test: 2 ppm (TDS of my pure RODI water)

Added and dissolved 0.33 g of CaSO4.2H2O. : 62 ppm (124 uS/cm).

Test 2:

Null test: 2 ppm

Added 0.28g of CaCl2.2H2O: 125 ppm (250 uS/cm).

That is twice the EC/TDS for equal amounts of Calcium when using CaCl2 over CaSO4. How or where am I getting this wrong, if so?

Cheers,
Michael

 

[Hanuman]

Hi @Hanuman, not sure how you came to the conclusion that CaCl2 would yield a lower EC/TDS compared to CaSO4 ? Your rarely off, so I ran a quick test just to make sure that I’m not off here either claiming CaSO4 also reduces your EC/TDS significantly (Im constantly on the hunt for reducing TDS so missing this would definitely make me go stand in a corner for 15 minutes ).

Targeting ~20 ppm of Ca in 1 US gallon (3.78L) of water:

Test 1:
Null test: 2 ppm (TDS of my pure RODI water)
Added and dissolved 0.33 g of CaSO4.2H2O. : 62 ppm (124 uS/cm).

Test 2:
Null test: 2 ppm
Added 0.28g of CaCl2.2H2O: 125 ppm (250 uS/cm).

I was about to ask you the same thing as to how you came to the conclusion that CaSO4 gives you lower TDS. In IFC's book this is not happening

CaSO4 - Total 67.9 TDS - 20 from Ca - 47.94 from SO4

CaCl2 - Total 55.4 TDS - 20 from Ca - 35.38 from Cl

That's a difference of 12.5 TDS in favor of CaCl2.

I also checked with Rotala Butterfly to make sure I was not full of it. Came out the same, except Rotala provides the S value (16) which equates to 47.9 ppm of SO4 which is what we find in the IFC Calculator.

To make sure I'm still sain:

CaSO4 ​

CaCl2 ​

Source: TDS and Electrical Conductivity - Lenntech

That is twice the EC/TDS for equal amounts of Calcium when using CaCl2 over CaSO4. How or where am I getting this wrong, if so?

Are you sure you have CaCl2 and not some other compound? Or perhaps that your CaCl2 is contaminated with something else?

Yesterday I changed my Ca source in my amano tank from CaSo4 to CaCl2 and the TDS went down. It was around ~ 417 uS/cm or so and it is now down to 380 uS/cm. Ok this is not a fair example as the lower TDS could also be due to the removal of nitrates and other elements.
I'll do a test tonight with my compounds to double check, just like you did. Maybe I'll get the same thing than you, else you might have to:

go stand in a corner for 15 minutes ).

Jokes aside I am happy to be corrected if I am wrong.

Sorry @D.Bezinski, we spoiled your thread with nerd chemistry

 

[Hanuman]

I'll do a test tonight with my compounds to double check,

Test was carried out.

Targeting ~20 ppm of Ca in 1L of water. Sorry, imperial units is not my thing
Amounts are minute so I used my analytical scale and weighed each compound 5 times to make sure I was not totally off. This said some inaccuracies are expected.

Test 1:
Null test RO water: ~7 ppm [500 scale] 16uS/cm
Added 0.086 g of CaSO4.2H2O. : 91 ppm (192 uS/cm) [Solution was allowed to rest a good 20 minutes and mixed multiple times to allow complete dissolution]

Test 2:
Null test RO water: ~7 ppm [500 scale] 16uS/cm
Added 0.073g of CaCl2.2H2O: 78 ppm (164 uS/cm)

--> That's 13ppm difference in favor of CaCl2

⚠️Now, one word of caution here, CaCl2 is highly hygroscopic hence why it's used as a desiccant. Could it be that my CaCl2 has absorbed so much water that the actual content of Ca and Cl per weight is technically lower? Possible.

 

[X3NiTH]

It’s a definite possibility that the compound has taken on some water, you can heat it to drive of the water of crystallisation to get you back closer to the anyhydrous compound and then re weigh the sample to see if there is a difference in weight from before heating, you can then retest to see if the TDS has changed any.

 

[MichaelJ]

Are you sure you have CaCl2 and not some other compound? Or perhaps that your CaCl2 is contaminated with something else?

The label on the plastic container (sealed with a screw-on lid) say this is 97% Calcium Chloride. Of course I can't rule out the product is somehow spoiled or contaminated.

Test was carried out.

Thanks for doing the test... Curious thing is that I have done this test on a couple of occasions, at least once combining it with an API GH test to gauge the actual Calcium level in the sample - not just relying on the EC/TDS measurement.

In light if your measurement I am seriously starting to doubt my sanity on this one.... I will have to redo it more rigorously later today.

--> That's 13ppm difference in favor of CaCl2

If I can replicate this I will take that over the CaSO4 at least in my soft water tank, and possibly go half and half in my shrimp tank. ... and of course go stand in a corner for 15 minutes.

Either way, I we will come to a conclusion!

Yes, big Sorry @D.Bezinski, for diverting your thread. We could ask the admin to move the relevant posts on this to a new thread: "CaSO4 vs. CaCl2: The Duel of the Fates" (ominous theme music playing)

Cheers,
Michael

 

[dw1305]

Hi all,

I'll see if I can find out.

Unfortunately above my pay grade, I think @MichaelJ posted some useful content a couple of months ago?

This may be of use <"The influence of ion composition of water on its electrical conductivity">?

cheers Darrel

 

[MichaelJ]

All right, I re-did the test. This time I targeted a fairly high 9 dGH (~64 ppm of Ca). And measured the GH using the API GH Test kit - counting the drops until the 5 ml solution in the test tube turns from yellow to green.

After applying the salt I would stir it, let it sit for 5 minutes and stir again... I did this 3 times so each test sample got about 15 minutes before measuring GH and TDS.

This time using 3 Liters of RODI water.

Test 1:

Null test: 2 ppm.

0.83 grams of CaSO4: 169 ppm (338 uS/cm). API test turned green on the 9th drop consistent with the target.

Test 2:

Null test: 2 ppm.

0.7 grams of CaCl2: 237 ppm (474 uS/cm). API test turned green on the 9th drop - but turned out somewhat darker green compared to the CaSO4 test, which somewhat suggests that the dGH might have been closer to 8 rather than 9 and I should have added slightly more CaCl2. Anyway, inconsequential for the overall result.

One curious thing about this is that the numbers aren't scaling linearly at all, as I would have expected.... relative to my first test I would have expected the CaSo4 solution at 64 ppm of Ca to yield closer to 200 ppm (64 ppm Ca / 20 ppm Ca x 62 ppm TDS) = 200 ppm . and the CaCl2 to be closer to 400 ppm. I can't explain this discrepancy - other than perhaps the TDS meter. Of course not many among us will target 64 ppm of Ca with RO water, so I guess it's more of academic interest, but still.

Either way, at least with the compounds I have in my possession, my TDS meter (Hanna Instruments), and how I did the test, it still appears that CaSO4 yields a significantly lower EC/TDS than CaCl2 for equal amounts of measured Calcium, but I am totally not comfortable about drawing a hard conclusion on this until we find an explanation for the discrepancy between mine and @Hanuman's measurements. Regardless of EC/TDS, the Calcium content (GH) is ultimately what we aim for here, but we also want to use the compound with the least collateral damage in terms of EC/TDS and this ought to be fairly predictable.

Cheers,
Michael

 

[Hufsa]

My other question is about section 5 of the Target Calculator. It's a bit confusing so I am not sure where I need to put 1.

If you havent seen it yet, check out the IFC calculator short guide, it touches on a few points such as the ratio field where you would often put the 1's.

View attachment 207153
Currently, I am not doing that.

Those are a part of the recipe for homemade ferts, so yes they are important to follow. I hope you are using RO/distilled water?
For macros it is not quite as essential as there is less potential for reaction between the salts, but you absolutely must acidify the micro ferts, otherwise things may precipitate and your fertilizer may become ineffective.

 

[D.Bezinski]

I hope you are using RO/distilled water?

Yes, I am.

If you havent seen it yet, check out the IFC calculator short guide

Thank you Hufsa. I will read it now.

 

[Hanuman]

0.83 grams of CaSO4: 169 ppm (338 uS/cm). API test turned green on the 9th drop consistent with the target.

This is far and above the solubility of CaSO4 by a very large margin. I did a similar test yesterday but then I scraped it because I realized I was over the solubility limits.
I'll redo the test myself heating up the CaCl2.

Personally, I don't think my tank is densely planted, so I am thinking EI Dosing Mid.

Personally I wouldn't use that dosing. I'd probably go for something like APT 3 specially if you have new soil.

My other question is about section 5 of the Target Calculator. It's a bit confusing so I am not sure where I need to put 1.
Potassium Nitrate (KNO3)
Magnesium Sulphate (MgSO4)
Potassium Phosphate (KH2PO4)
Potassium Sulphate (K2SO4)

You put a 1 to the compound you want to use. Those stated above look fine to me. Maybe you can get away without Potassium Sulphate. You have to check if your target is met at 100%.
For Mg this is added by two means. Through the fertilizer and through your remineralizer. For fertilizer purposes it's usually minimal (refer to the cloned fert). The bulk of the Mg is added as remineralizer when doing your water change. For Ca, never add that to your fertilizer. ONLY use it as a remineralizer when doing WC.

And lastly... How important is this:

I would say, very specially for micros. You can get away by not adding it to the macros, but with micros, definitely you need to and it needs to added BEFORE adding any other compound.

 

[Hanuman]

This is far and above the solubility of CaSO4 by a very large margin.

Scrap that. I was looking at the wrong column. Solubility is fine.

 

[MichaelJ]

This is far and above the solubility of CaSO4 by a very large margin. I did a similar test yesterday but then I scraped it because I realized I was over the solubility limits.
I'll redo the test myself heating up the CaCl2.

Not entirely sure if you're joking... the solubility limit for CaSO4 is 2.6 grams per liter... I would have to target a whopping 600 ppm of Calcium to hit that limit.

Cheers,
Michael

 

[MichaelJ]

Scrap that. I was looking at the wrong colum. Solubility is fine.

Ok, just saw this... never mind my commend above.

PS: if I would be hitting any limits I wouldn't be able to measure the 9 dGH with the test kit.....

Cheers,
Michael

 

[LMuhlen]

At the risk of further derailing the topic into, as it was called, "nerd chemistry", but considering the issue at hand, that is the desire to reduce conductivity for shrimps that supposedly have an issue with osmoregulation, if you are going into the very specific effects of Ca salts into conductivity, I think it is important to rethink this conductivity and shrimps thing. As I see it, conductivity is important to shrimps as a way to indirectly estimate the concentration of salts, as they don't particularly care about conducting electricity and more about keeping their own internal salts at comfortable levels. So instead of worrying about how SO4-- and 2Cl- affect conductivity, it would be more effective do discuss what is easier to osmoregulate, if a single SO4 ion or 2 Cl ions.

 

[MichaelJ]

At the risk of further derailing the topic into, as it was called, "nerd chemistry", but considering the issue at hand, that is the desire to reduce conductivity for shrimps that supposedly have an issue with osmoregulation, if you are going into the very specific effects of Ca salts into conductivity, I think it is important to rethink this conductivity and shrimps thing. As I see it, conductivity is important to shrimps as a way to indirectly estimate the concentration of salts, as they don't particularly care about conducting electricity and more about keeping their own internal salts at comfortable levels.

Thats the general understanding, yes. But the same can be said for fish, and really not many of our soft water fish originate from habitats with a higher mineral contents than say 150 uS/cm. - with many habitats down in the 20-50 uS/cm.

So instead of worrying about how SO4-- and 2Cl- affect conductivity, it would be more effective do discuss what is easier to osmoregulate, if a single SO4 ion or 2 Cl ions.

It's a very good question. I have wondered about this myself... I certainly do not know the answer. I only have this blunt instrument called EC or TDS to gauge that and most experiences and literature points in the direction of keeping EC in check to provide optimal conditions - and so far its been working for me. I tend to go by the chemical markup of the species natural habitats - this is by and large futile, but I am trying. For instance, in my densely planted low-tech shrimp tank I keep the GH at ~5.5 (KH ~ 0.5) ... this leaves me very little headroom for fertilizers and even though I am dosing quite leanly in this tank (with no deficiencies or algae) I haven't been able to sustain an EC much lower than 200 uS/cm (100 ppm TDS). After a WC it usually sit around 190 uS/cm).

I believe @LondonDragon will move the CaCO4 vs. CaCl2 related posts to a different thread. And there are certainly more to come on the topic.

Cheers,
Michael

 

[D.Bezinski]

Hi All,
After reading Hufsa's guide, these are the results for my Macros and Micros.

Macro:

Micro:

In regards to the RO water remineralization, I've decided to go with CaCl2 and MgSo4, however, I am not sure about the ratio ( CaCl2: MgSo4 = 3 :1 and add to my water until I get 5dGH ? ). Sorry for asking that many questions here... I am just changing too many things at once

Regards
Dimitar

 

[MichaelJ]

Hi All,
After reading Hufsa's guide, these are the results for my Macros and Micros.

Macro:
View attachment 207187
View attachment 207188

Micro:
View attachment 207189

In regards to the RO water remineralization, I've decided to go with CaCl2 and MgSo4, however, I am not sure about the ratio ( CaCl2: MgSo4 = 3 :1 and add to my water until I get 5dGH ? ).

Not sure what makes you want to use CaCl2 in lieu of the information above … but certainly, 3:1 Ca:Mg will work regardless of your choice of salts. And 5 dGH is perfect for just about any critter - except those that specifically require hard water or if you want to breed delicate soft water species.

Cheers,
Michael