KH/pH/CO2 question

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Drewbacca

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Mar 20, 2019
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I’ve just recently gotten into the CO2 injection process. I have a pH controller hooked up to my solenoid valve... excessive, I know, but I got a great price on the setup. Anyway I’m having trouble getting some of my more CO2 dependent plants to take off. My KH is 4. However, I have mollies in there and they like more alkaline water. I’ve read that the lowest pH they are comfortable with is 7, and that’s pushing it. I also have some snails in there that don’t like lower pH. The problem is that even at 7, my ppm of CO2 isn’t that great (I’d like a goal of 25). I’d need to drop it down to around 6.67 to get it where I need it... and I don’t think my fish would like that. I read a mistaken page recommending Wonder Shells to raise KH and GH, but it only really does the GH. Anyway, I’m now considering adding in baking soda to raise the KH.

So, here’s my question. If my CO2 system will kick in to keep the pH from rising, will that allow me to raise my KH by itself and thus my ppm of CO2? Or will injecting CO2 counteract any raising of the KH?

I love the math behind this but I fear I’m overthinking things.
 

fishorama

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Jun 28, 2006
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SF Bay area, CA
Well, while I've never tried co2 (although I have all the "stuff") I would say you need to add GH & maybe KH. It can be as easy as adding some crushed coral in your filter (for GH) & some baking soda for KH at each weekly water change. The exact numbers are more problematic to a dose of either. It's a matter of tap water, substrate, etc...All a balancing act...
 

Drewbacca

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Mar 20, 2019
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I’ve been adding the GH with the Wonder Shell. It’s gone from 9 to 11, which is where I’d like to get the KH to eventually. I read a few articles that I should just ignore pH and shoot for the needed CO2 level, but at my KH I’m worried that would hurt the mollies and snails due to how low the pH would have to go.
 
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