CaCl2 vs CaSO4?

[mn_aquascape]

Any thoughts on the differences between these and why you might pick one or the other?

I just started using APT sky and it is a super fine powder and super pure white. It makes me suspect that it is ground up/pulverized CaCl2, because CaSO4 has been more off white or grey in my experience.

I'm going to hang with APT sky for a while in my main plant display - it has some 'extra goodies' in it that might be worth it. But it is making me rethink my mineral plan in my other large fish displays (with some plants) where I run RO water. Current mineral mix is CaSO4 and MgSO4, but I'm not very precise with it and I feel like I've got a ratio that isn't helping me.

The APT sky dissolves so nicely and the results I've noticed in my main planted display in the first couple weeks is making me wonder about doing something different in my planted fish displays.

What can you all share with me about CaCl2 vs CaSO4?

--Steve

 

[Art]

Hi Steve,

Great question. I will give you my answer based on things I've read over the years and experience. I'm not a chemist. I hope we end up finding a true chemist in our midsts so that he/she can blow our minds with the true chemical science behind these types of questions!

The obvious difference between the two is the chloride versus the sulfate. Both are needed by plants, one generally considered as a macronutrient and the other as a micronutrient. Both may be in your tap water, if you use that.

Another obvious difference is that CaCl2 is much more thermogenic than CaSO4 so it will increase the temperature of the water considerably. I mean significantly as I've read people reading 110F - 140F. Not good for your fish if you are dumping it into an aquarium as opposed to premixing.

The solubility of each differs but I don't think that would make a big difference to us. We usually pre-mix the Ca component of our DIY mixes so yes, it's a difference, but really not one that matters much.

As for the APT Sky, I went and saw that Dennis is saying that it helps people with hard water keep soft water plants. I suspect he means that this somehow plays with the carbonates in the water. I am then suspecting calcium carbonate CaCO3 or calcium gluconate.? However, if it so easily dissolved, maybe it's calcium acetate but then I don't see how it could be helping keep soft water plants in hard water. Hmm, perhaps we can ask Dennis?

In the end, both CaCl2 and CaSO4 will both add Ca to your water. Depending on what else you're adding, perhaps one fits better into your overall regimen than the other because one will provide more Ca per ppm. Does that matter? Up to you.

I think the vast majority are using CaSO4. However, if your micro formula doesn't contain chloride, you may want to consider adding CaCl2 into your regime. Any of the calculators will factor in the difference between the two.

Anyone else have any thoughts?

#CaCl2

 

[GreggZ]

I think the vast majority are using CaSO4. However, if your micro formula doesn't contain chloride, you may want to consider adding CaCl2 into your regime. Any of the calculators will factor in the difference between the two.

This is exactly what I do. CaSO4 for raising dGH, then a small amount of Calcium Chloride added to my micro mix.

IME of all the things to worry about dGH is low on the scale. Think enough but not too much.

 

[mn_aquascape]

Thanks guys! I think I'll just keep it simple then with APT sky or my main display for now, and CaSO4 and MgSO4 for my bigger planted fish tanks - just start being a little more precise in my measurement.

Also, I do premix the Sky in a small container before adding to the tank. It is definitely exothermic, but not more than making a cool glass of water feel slightly warm.

--Steve

 

[Art]

Checked with Dennis, he says it's CaSO4.