# co2 question



## pyrrolin (Jan 11, 2012)

Just want to double check something about co2 diffusion. I know when c02 is working well the ph will go down. But if the co2 is not being diffused well, will the ph still go down?

I just setup DIY co2 on two identical tanks and I'm about to check the ph to see if both have dropped hoping this will give me an indication of how well my system is working if that alone can give me a bit of an indication.


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## pyrrolin (Jan 11, 2012)

ok, that didn't work so well, the normal ph here is about 7.4 so I did a test of normal range that goes up to 7.2 and its 7.2 at least ph.

Maybe I'll test again tomorrow before I turn the lights on as the lights have been on for many hours now and the co2 may have been used up.

I would love to just use little pumps to diffuse it as I find that way works great but there are 5 tanks I want to do and I don't want to have that many extra things plugged in, hydro bill is high enough as it is.


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## coldmantis (Apr 5, 2010)

if you have a kh tester then just do this test and you will know how much co2 your tank is getting and whether you should add another bottle or not.

http://www.aquascapingworld.com/magazine/images/stories/Issues/July2008/pH_KH_Chart.jpg


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## aniroc (Aug 23, 2012)

Measure the pH. Take a sample of tank water, let it sit for 24 hours in a cup. Measure the pH of the sample. The difference in pH (if any) is given by outgassed CO2. 
The temperature could give you some errors (CO2 is more soluble at lower temperatures) but the experiment will give you a better idea than the chart


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## charlie1 (Dec 1, 2011)

aniroc said:


> Measure the pH. Take a sample of tank water, let it sit for 24 hours in a cup. Measure the pH of the sample. The difference in pH (if any) is given by outgassed CO2.
> The temperature could give you some errors (CO2 is more soluble at lower temperatures) but the experiment will give you a better idea than the chart


+ 1
I will add if you have a difference of 1 PH unit you are close to optimal saturation, you then tweak by observation from there on.


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## pyrrolin (Jan 11, 2012)

So ph change is a good indicator then? Setup on 2 more one is working great, ph dropped, other not so well, moved it to another power head, should improve. My main problem is the first 2, no pump to diffuse them and I have sponge filters


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## pyrrolin (Jan 11, 2012)

trying a couple experiments on the tanks with sponge filters. One has a bubble wall thingy on it now, I think it will make small bubbles, will see in a while. On the other I just shoved a little filter floss into the end of the tube, again, will see in a while how that works. Waiting to break a cigarette or something to use a filter, don't want to just waste one.


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## Darkblade48 (Jan 28, 2008)

The pH/kH/CO2 relationship can work, under ideal conditions. Depending on your water chemistry, you may find that you are overestimating your CO2 (if you have humic and/or tannic acids, it will tend to lower your pH, giving you higher than anticipated levels of CO2).


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## pyrrolin (Jan 11, 2012)

because of the sponge filters in some of the tanks, I am not worried about too much co2, just trying to get some extra in the tank to help the plants a bit. Not optimal, but I guess every bit helps


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