CaCl2 question

daveedka

daveedka

Purple is the color of Royalty
Jan 30, 2004
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Columbus, ohio
I highly suspect that I could use more calcium in my tank. My tap water is very low, I have been using CaCo3 in various form to raise my Kh, but my snails shells still show a lot of erosion, my plants in the big tank still show a lot of signs of calcium defeciency, and the cuttlebone I put in for the snails is under constant attack by the snails and of course the pleco who investigates everything via the digestive track.
CaCl2 is easy to find I have some in the garage. How much should I use, how do I know how much is too much. I am running crushed coral in the filter, and the change water has CaCo3 in it as well. My Kh still stays at about 4degrees. Tap is 2-3 degrees tops.
I assume I should start slow, but don't know what point to start at.
Dave
 
The java fern. in particular is growing deformed and and I get a lot of yellow edges. Leaf size is what I would call minimal compared to my other tanks, My other tanks have similar symptoms, but not nearly as severe. the other tanks also get a lot more calcium supplement via high calcium food for the snails. Kh runs 1-2 degrees higher in the other tanks than it does in the 115. all tanks have crushed coral in the filters, which I am still working on adjusting. but the coral takes a ridiculous amount of time to find a stable level. I can up the quantity and it will be 4-5 weeks before I see a change in the KH. I thought the Calcium chloride might speed things up a tad, and since I have some "heet" in the garage, I was going to steal some for the tank.
Am I barking up the wrong tree here?
 
Well, you could use 1.1 times as much CaCO3 as you would use CaCO3
Click to expand...

Was that a typo, or a stab at the insanely obvious :laugh: :laugh:

Since my Kh is at a level I am comfortable with, I thought it would be easier faster, and probably better to just target calcium via calcium chloride rather than to try to raise the calcium level via calcium carbonate. The other issue with dosing calcium carbonate lies in the fact that I don't know the dissolution rate, I only know the contralled quantities I add to the system, much of which is still laying in the filter and the bottom of my change water barrel. so how much I actually added to the water column is unknown.
Additionally, the tanks that are doing the best (with Kh and Calcium) are utility tanks which have the crushed coral mixed into the substrate, above my RFUG's. The problem tank is a show tank, and I don't want the white specs showing up in the substrate. All Crushed coral in that tank is in the filter out of sight. According to my research there is a drastic difference in effect between the two different applications, influenced by bio-film water flow etc.
Dave
 
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Wooops! <fills second cup of cofee> Must be a Monday! Yeah, 1.1 times as much CaCl2 would give you the same amount of Ca as CaCO3, I'm talking by weight since I assume that you're thinking in ppm's not moles/L.

Two ways to increase CaCO3 dissolution are to decrease temperature, which probably wouldn't have too much effect over the range you have to work with, and increase CO2 concentrations.

CO3 + CO2 + H2O = 2HCO3

So by pushing up CO2, you pull more CO3 into bicarbonate, which will then pull:
CaCO3 -> Ca + CO3 to the right, increasing your Ca levels.

I've got to give it some thought, and lord knows I'm not that swift on Monday mornings, but I'm not sure whether adding CaCl2 will actually increase the Ca in your tank very effectively or whether it will simply add a forcing to the right side of CaCO3 dissolution, basically acting like a buffer would in an acid-base system. But maybe I'm overthinking this...
 
I read on plantgeek that Tom Barr doses about 1/4 teaspoon per 25 gal of CaCl2. I've just started using this because I was getting cupped leaves on my sword and java ferns. It's a bit early to say how effective this will be.

How's your nitrate Dave? My tap water is through the roof.
 
How's your nitrate Dave? My tap water is through the roof.
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HAven't checked my tap water lately, It would be really nice if my tap water nitrate went up considering I just totally re-wrote my dosing plan to increase nitrates. Phosphates from the tap are down, and according to the folks at Byerly's, It is common for Our tap water to have big PO4 swings.

I've just started using this because I was getting cupped leaves on my sword and java ferns. It's a bit early to say how effective this will be.
Click to expand...

Sorry you're having trouble also, but it's nice to know I'm not the only one on this water source with signs of low calcium.

I've got to give it some thought, and lord knows I'm not that swift on Monday mornings, but I'm not sure whether adding CaCl2 will actually increase the Ca in your tank very effectively or whether it will simply add a forcing to the right side of CaCO3 dissolution, basically acting like a buffer would in an acid-base system. But maybe I'm overthinking this...
Click to expand...

It may take more than an extra cup of coffee for me to process that. I'll go get another cup, and come back and read it agian. :laugh: :laugh:

Dave
 
Like I said, I'm probably overthinking it...

What I was getting at is you have two dissociations:
CaCO3 -> Ca + CO3 (1)
and
CaCl2 -> Ca + 2Cl (2)

Reaction (2) will happen immediately, at least, I think that the dissociation should be complete and instantaneous in any low Ca/Cl aqueous solution.

Reaction (1) can go both ways. The direction of dissociation will depend on pH (which affect the carbonate/bicarbonate equilibrium), CO2 concentrations (which reacts with CO3, see above, and influences pH), and CO3 and Ca concentrations. And other things like temperature and pressure also play roles.

By increasing concentrations of Ca, you add a 'buffer' to reaction (1), like in an acid-base system:
AH -> A- + H+ (an acid and it's conjugate base)
which can be buffered by adding:
KA -> A- + K+ (a salt of the conjugate base)

In this situation changes to H+ will be balanced by the presence of excess A-, so pH won't fluctuate. I think that something similar is possible with the first two reactions, but now that I've had a little more time to think about it, the effect will be to buffer CO3 levels, not Ca levels. Since you're adding the Ca salt, your Ca levels will increase and will buffer your CO3 concentrations, I think.

Anyway, the bottom line is that adding CaCl2 will increase your Ca concentration, which is what you're gunning for.
 
You have low Ca levels in your tap water in OH?
The ground water rock ias Karst which is mainly CaCO3 eg => limestone.

I get CaCl2 at a pool store down the road, gregwatson also carries it.
You do not need that much to provide enough for plants.

Regards,
Tom Barr


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