# Why is CaCl2 better than CaCO3 ?



## kekon (Aug 1, 2005)

Is it only because CaCl2 dissolves better in the water than CaCO3 ? (CaSO4 is recommended together with CaCl2 but it dissolves hard in the water, similarily as CaCO3). Viewing all the threads about preparing RO water I came to the conlusion that the following "set" is a good thing to mineralize RO water:

CaCl2, CaSO4, MgSO4, NaHCO3.

As far as I know CaCl2 and CaSO4 should be mixed in 4:1 ratio but I couldn't find how much NaHCO3 should be added.


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## cS (Jan 27, 2004)

kekon said:


> (CaSO4 is recommended together with CaCl2 but it dissolves hard in the water, similarily as CaCO3)


You're probably confusing CaSO4 with MgSO4. 

CaCl2 and MgSO4 are recommended to be used together to increase GH (the measure of Ca & Mg). CaCl2 is preferred over CaCO3 and CaSO4 because CaCl2 dissolves in water very easily.

The 4:1 *Ca:Mg* ratio is quoted often but I wouldn't give it much thought because the Ca & Mg content of natural water vary greatly. Just add equal amounts of Ca & Mg to bring the GH >=3 degrees and your plants would be just fine.

NaHCO3 (baking soda) is used to increase KH. 1 teaspoon (6 gram) per 50 liters of water will increase the KH by 4 degrees.


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## Salt (Apr 5, 2005)

If you are referring to the articles Edward has written, I'm confused by it also. I don't see where he is testing his water and checking his levels. It looks to me like he is adding a bit of this and a pinch of that every couple of days. Following that, it follows to me that CaCl2, CaSO4, and MgSO4 would yield the best results doing it this way, because you are adding additional nutrients that plants need, mainly sulfate and chloride. If you use only CaCO3 and MgCO3 and basically just "add a spoon" every few days without tracking your carbonate levels, then you could be raising your carbonate levels to be too high for some species of plants that are more fussy about carbonates, plus if you are not adding anything else, then the plants will lack chloride and sulfate.

I use very pure RO/DI water (from a 5 stage system), plus I use the Seachem line of plant products. To reconstitute on my 40% weekly water change, I use a gram scale and use CaCO3 and MgCO3 for GH/KH. The Seachem products also increase the GH a little over the week, so at the next weekly water change, adding CaCO3 and MgCO3 to reach my target levels (5 dKH and 6 dGH) will leave the KH a little low, so I make up the remaining CO3 by adding KHCO3. All this adds *only* calcium, magnesium, potassium, and carbonates, and allows chloride, sulfate, and sodium to come from the Seachem products. This also helps lower TDS, which is also helpful in growing plants.

So far I have gotten excellent results, better than I ever did with CaCl2 and MgSO4. I even got some emerged _pogostemon stellata_ a couple of weeks ago and lo and behold it's growing!  A personal first.

Based on a lot of what I have been reading lately, I am currently thinking that the limiting factor in growing some of the tougher plants are 1) too much carbonates, and 2) too much magnesium. With the recent discovery (by Edward and Tom Barr) that 10 ppm or higher of magnesium stops _rotala wallichii_ and _toninia_ from growing completely, I think that the ca:mg ratio becomes much more important if you are trying to grow species such as this.


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## Mjproost (Nov 17, 2005)

> adding CaCO3 and MgCO3 to reach my target levels (5 dKH and 6 dGH)


Salt- Thanks again for your help. How do you get the CaCO3 to dissolve?

I have some of this and it doesn't seem to dissolve in a reasonable amount of time for me.


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## Salt (Apr 5, 2005)

CaCO3 is only slightly soluable in RO/DI water at room temperature. You can apply heat to raise the solubility somewhat, or, more effectively, you can inject CO2 while you are mixing it to turn it into Ca(HCO3)2 - calcium bicarbonate, which only forms in solution, and _is_ soluable. (Don't apply heat *and* inject CO2 at the same time, or you'll actually lower solubility.)

In my case, I use a magnetic stirrer which helps a lot, and inject CO2 from my spare 5 lb tank using a sweetwater fine pore airstone. It still stays milky, and turns my tank water opaque white when I add it. But my tank has very good flow, and if I add it during the day while CO2 is being injected, it completely dissolves and the water goes back to clear within 60 minutes.


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## kekon (Aug 1, 2005)

cS said:


> You're probably confusing CaSO4 with MgSO4.


No, I'm not cunfusing CaSO4 with MgSO4. CaSO4 was written about by Edward as a suplement to CaCl2. Besides, when I had GH about 7 my plants grew quite well. When I began to use KNO3 and KH2PO4 at GH = 3 something wrong has happened - curled, deformed and stunted leafs on many plants which suggests that it's Ca/Mg deficiency. The total growth was stunted. Many plants have very light-green (they're almost yellow). The mixture used to prepare RO water consits 13 ppm Ca and 4 ppm Mg (it's ready to use commercial solution called "Hydro Mineral" and produced in my country Poland).

Well, apart from what I've just written I want to use CaCO3 or CaCl2 and NaHCO3, MgSO4 to mineralize RO water. What levels of Ca, Mg, HCO3, SO4 should I have ?


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## Edward (May 25, 2004)

kekon said:


> Well, apart from what I've just written I want to use CaCO3 or CaCl2 and NaHCO3, MgSO4 to mineralize RO water. What levels of Ca, Mg, HCO3, SO4 should I have ?


20 - 30 ppm Ca 
5 ppm Mg
KH depending on preferred pH
SO4 ignore


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## kekon (Aug 1, 2005)

I wonder if high level of Cl coming from CaCl2 will not harm plants :-?


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