tiger15

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

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

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

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

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

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

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.

Attached Thumbnails

 

davemonkey

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

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

GadgetGirl

What does a plant with calcium deficiency look like?