# Testing CaCO3 Effect on Plants



## hoppycalif (Apr 7, 2005)

I found a cheap source of calcium carbonate on Amazon, so I want to see if adding calcium and carbonates to the water will improve plant growth, when STS substrate has stripped most of the original calcium and carbonate from the water. I added one teaspoon of CaCO3 to the water on the left side tank, raising the KH from 1 dKH or less to 3 dKH. The effect on GH was much less, but I'm still testing GH to be sure of that.

My expectation is that the increased carbonate will increase the stem plant growth. No CO2 is being added, so there is likely less than 3 ppm of CO2, so the added carbonate may help stem plants.

Each tank has essentially identical plantings.


----------



## mistergreen (Mar 3, 2007)

How much pH was raised?


----------



## hoppycalif (Apr 7, 2005)

mistergreen said:


> How much pH was raised?


Tank without CaCO3 pH is 6.0 or a bit less. With the CaCO3 pH is 7.2.

GH, with CaCO3 is 5 dGH. Without CaCO3 is 3 dGH.


----------



## mistergreen (Mar 3, 2007)

Wow, a whole 1.2


----------



## GadgetGirl (Sep 25, 2013)

Is calcium carbonate a substitute for baking soda? I'm assuming to eliminate the sodium in baking soda (sodium bicarb).


----------



## hoppycalif (Apr 7, 2005)

Sodium bicarbonate adds sodium to the water, which isn't bad, but if you also want to add calcium I figured that adding calcium carbonate might be interesting. I know it may not work well, since I think carbonates in water are always bicarbonates, so a chemical reaction has to occur when you add calcium carbonate, and I'm not sure what the reaction is. I assume it gets hydrogen from the water, and the leftover oxygen joins the calcium to form calcium oxide. (You may recognize that I am not a chemist.)


----------



## mistergreen (Mar 3, 2007)

I think this is what you mean

CaCO3 + H2CO3 ↔ Ca(HCO3)2 ↔ Ca2 + 2 CO2 + 2 OH


----------



## hoppycalif (Apr 7, 2005)

When I added the calcium carbonate into the water the water became very milky, especially when I stirred it up a bit. Over night it cleared up, but a few white clumps were on the substrate. I stirred them a bit and the water became a little milky, but quickly cleared up.

I just googled this subject and it says that calcium carbonate will not dissolve in water! To say I am confused would be an understatement.


----------



## mistergreen (Mar 3, 2007)

CaCO3 will dissolve only in certain conditions like the formula above or with other acids. Your water was 6.0 so it had some acid in it.


----------



## hoppycalif (Apr 7, 2005)

Thank you!! Now it makes some sense.


----------



## tiger15 (Apr 9, 2017)

mistergreen said:


> I think this is what you mean
> 
> CaCO3 + H2CO3 ↔ Ca(HCO3)2 ↔ Ca2 + 2 CO2 + 2 OH


The above reaction will take place only if you inject CO2, carbonic or other acid. Without acidification, no spontaneous release of CO2 will occur. Some hard water plants, such as Vals, are able to split CaCO3 to extract carbon.

CaCO3, a component of limestone, is barely soluble in neutral to alkaline water. The solubility of CaCO3 increases with acidification, and acid test is one way to identify limestone by observing bubbling CO2.

Adding CaCO3 will increase both kH and gH, but won't increase carbon availability to plants except Vals and a few hard water plants.


----------



## mistergreen (Mar 3, 2007)

Yeah. The H2CO3 reaction will occur in natural systems too like rain collecting CO2 in the atmosphere. An aquarium doesn’t have the luxury unless you inject CO2.


----------



## mistergreen (Mar 3, 2007)

tiger15 said:


> The above reaction will take place only if you inject CO2, carbonic or other acid. Without acidification, no spontaneous release of CO2 will occur. Some hard water plants, such as Vals, are able to split CaCO3 to extract carbon.
> 
> CaCO3, a component of limestone, is barely soluble in neutral to alkaline water. The solubility of CaCO3 increases with acidification, and acid test is one way to identify limestone by observing bubbling CO2.
> 
> Adding CaCO3 will increase both kH and gH, but won't increase carbon availability to plants except Vals and a few hard water plants.


I was thinking. CaCO3 can't exist in a solution for plants like val to utilize. It will precipitate out of solution. However, Ca(HCO3)2 is only in solution.


----------



## hoppycalif (Apr 7, 2005)

When I mixed in the CaCO3 powder the water became very milky - meaning the particles were causing the milky look? And, after several hours the water cleared - meaning the particles settled into the gaps in the STS substrate? If so, I did the equivalent of putting a thin layer of CaCO3 under the STS? Maybe putting a thin layer at the bottom is the best use of that material. Or, maybe the best use is as a paper weight?


----------



## kekon (Aug 1, 2005)

hoppycalif said:


> When I added the calcium carbonate into the water the water became very milky, especially when I stirred it up a bit. Over night it cleared up, but a few white clumps were on the substrate. I stirred them a bit and the water became a little milky, but quickly cleared up.
> 
> I just googled this subject and it says that calcium carbonate will not dissolve in water! To say I am confused would be an understatement.


Regular CaCO3 powder has relatively large grain size that makes it hard to dissolve. When poured into the water part of it falls down to the substrate where it stays for long time before it dissolves completely. There is also so called "ultra-fine" CaCO3 on the market that has extremely fine grain size. In such a form it floats in the water column and never falls down to the bottom. It forms steady suspension ("milky water") that will dissolve in no longer than a few hours (the more CO2 the faster it will dissolve). You can also make ultra-fine CaCO3 by yourself (albeit it will not be as good as one purchased from manufacturer). The trick is to use ceramic kitchen mortar and put small amounts of CaCO3 and grind it intensely (this is not pleasant work though...).


----------



## davemonkey (Mar 29, 2008)

Following. 
Sort of a side question: did you initially find any sort of calcium or iron (or other) deficiency in the plants panted within STS?
I am currenlty having an issue with what I *think* is iron or calcium deficiency (will finally break down and get some test strips soon) in my STS (rather, Oil Dri) tank, despite moderate light and EI dosing. 
I am wondering if the substrate has stripped those nutrients from the water column until the substrate has been "satisfied".


----------



## hoppycalif (Apr 7, 2005)

davemonkey said:


> Following.
> Sort of a side question: did you initially find any sort of calcium or iron (or other) deficiency in the plants panted within STS?
> I am currenlty having an issue with what I *think* is iron or calcium deficiency (will finally break down and get some test strips soon) in my STS (rather, Oil Dri) tank, despite moderate light and EI dosing.
> I am wondering if the substrate has stripped those nutrients from the water column until the substrate has been "satisfied".


I have found low KH and GH with all of my STS substrate set-ups. Apparently a high CEC material as a substrate will absorb calcium ions and its attached carbonate ions. I can't prove that is a problem, but it did arouse my interest is seeing what would happen if I added a lot of both calcium and carbonates.

Attached is a pic of the tanks this morning. I don't see anything yet that convinces me that the left tank, the one with the calcium carbonate, is doing significantly better.


----------



## davemonkey (Mar 29, 2008)

hoppycalif said:


> I have found low KH and GH with all of my STS substrate set-ups. Apparently a high CEC material as a substrate will absorb calcium ions and its attached carbonate ions. I can't prove that is a problem, but it did arouse my interest is seeing what would happen if I added a lot of both calcium and carbonates.
> 
> Attached is a pic of the tanks this morning. I don't see anything yet that convinces me that the left tank, the one with the calcium carbonate, is doing significantly better.


I wonder if, for this experiment, you'd almost need to start both tanks with plants showing nutrient deficiency? Then see if the added calcium carbonate improves nutrient uptake in an STS substrate.

I would love to run such a test. But I am not set up for comparing (to this degree). I DO, however, have plants showing deficiency, and I do also have Calcium sulfate (in Seachem Equilibrium). I'll take some "today" shots of my white-leaved crypts and then see what happens after some regular calcium addition. (Test strips currently in the mail, and will help me track changes to hardness, so I don't overdo it.)


----------



## hoppycalif (Apr 7, 2005)

davemonkey said:


> I wonder if, for this experiment, you'd almost need to start both tanks with plants showing nutrient deficiency? Then see if the added calcium carbonate improves nutrient uptake in an STS substrate.
> .........


I'm not clear about how starting with nutrient deficiencies would help. Can you explain?


----------



## GadgetGirl (Sep 25, 2013)

What does a plant with calcium deficiency look like?


----------



## kekon (Aug 1, 2005)

GadgetGirl said:


> What does a plant with calcium deficiency look like?


Young leaves are twisted, tips are dwarfed, slow growth.
Many deficiencies look similar, and it might be difficult to tell one from another.

https://mbfi.co.za/deficiency-guides/


----------



## hoppycalif (Apr 7, 2005)

It looks like the left tank, the one with the calcium carbonate, has more and better growth than the right tank. Today I had to prune the Pogostemon Stellatus because it was at the top of the tank, so I cut it in each tank, at about the same height, and replanted the cuttings.

Water Parameters are: With Calcium Carbonate - pH=6.6, KH=3 DKH, GH=4 DGH. Without Calcium Carbonate - pH=6.0, KH=1 DKH, GH=3DGH
Apparently the Calcium Carbonate has become more absorbed by the substrate.


----------



## hoppycalif (Apr 7, 2005)

This test is not going to work! I forgot a critical factor: the Liebig law of the minimum, which is that plant growth rate is determined by the nutrient which is the lowest compared to what the plant requires. If you set up two identical tanks, both of which have a nutrient available which is the lowest, compared to what the plants need, adding more of any other nutrient to one of the tanks will not make the plants in that tank grow faster. Almost always the nutrient that is available which is the lowest compared to what the plants need is carbon - CO2.

I originally made this divided 10 gallon tank to try to see what can make algae start growing, not to test nutrients. So, I need to do that only. (Since this is a hobby, the fact that this has been fun is the most important thing!)


----------



## mistergreen (Mar 3, 2007)

I'm surprised you haven't grown more algae. Stronger light?


----------



## hoppycalif (Apr 7, 2005)

If algae starts growing only if there is enough available iron in the water I shouldn't have algae, since I am dosing both tanks with relatively low amounts of trace elements. I can try to verify this by adding some Flourish Iron to one tank, every day or two. This appeals to me, except I am enjoying the pair of tanks now, and making one grow algae wouldn't enhance my enjoyment.


----------

