# Keeping a stable PH with CO2



## TorontoPlantMan (Aug 16, 2013)

Hey guys, 

I've been looking into getting a real CO2 setup for awhile and I'm almost there but I just have a question...I know you can purchase a PH monitor to stabilize your PH but there really quite expensive, in some cases more then the whole CO2 setup itself. So I'm just wondering how you guys who are not using PH monitors are keeping a stable PH once your lights and CO2 go off at night. I always hear about guys saying they can change there PH from X to X within an hour or two and I can't imagine that PH swings like that are very good for the fish or the plants..Can anyone explain?

Thanks a lot


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## pyrrolin (Jan 11, 2012)

I have never heard of the ph going up and down like that.


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## k2x5 (Mar 12, 2008)

I've personally never used a pH monitor on any of my planted tanks. My 55g with pressurized CO2 does great without me worrying about the pH going up at the end of the day when the CO2 stops and the lights go off.

After the CO2 has been on for 1-2 hours, my pH is down about 0.6 and it stays rock solid through the day with constant CO2 input; abut 1-2 hours after CO2 turns off it slowly goes back up to the starting day numbers.

The only thing I can think of that would fluctuate as much as you've described is a poor solution of DIY Yeast CO2 that isn't putting out a constant output, or a bad diffusion method.


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## solarz (Aug 31, 2010)

PH shifts from CO2 will not cause any harm to livestock. I've ran DIY CO2 many times in the past and it has never caused any issue.


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## TorontoPlantMan (Aug 16, 2013)

pyrrolin said:


> I have never heard of the ph going up and down like that.


I'll find the OP who I saw say that and show you. I'm pretty sure he/she said their PH changes a full point "6.0-7.0" within an hour.



k2x5 said:


> I've personally never used a pH monitor on any of my planted tanks. My 55g with pressurized CO2 does great without me worrying about the pH going up at the end of the day when the CO2 stops and the lights go off.
> 
> After the CO2 has been on for 1-2 hours, my pH is down about 0.6 and it stays rock solid through the day with constant CO2 input; abut 1-2 hours after CO2 turns off it slowly goes back up to the starting day numbers.
> 
> The only thing I can think of that would fluctuate as much as you've described is a poor solution of DIY Yeast CO2 that isn't putting out a constant output, or a bad diffusion method.


Interesting, thanks for the input.



solarz said:


> PH shifts from CO2 will not cause any harm to livestock. I've ran DIY CO2 many times in the past and it has never caused any issue.


I'm not asking about DIY CO2. I'm asking about pressurized


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## solarz (Aug 31, 2010)

TorontoPlantMan said:


> I'm not asking about DIY CO2. I'm asking about pressurized


CO2 is CO2. I mentioned DIY because unlike pressurized, you can't turn DIY CO2 off at night. If CO2 pH fluctuations caused any harm, my fish would have died a long time ago.


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## aniroc (Aug 23, 2012)

PH fluctuation because of CO2 level is not harmful to fish because TDS is not affected. In fact, any planted tank will have lower pH in the morning, before lights are turned on.
Its the osmotic pressure fluctuation that stress fish, not pH itself.


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## Fishfur (Mar 4, 2012)

Fwiw, in native habitats, parameters can and do change, every night and day, not to mention the effects of seasonal change and storms. In daylight, plants give off oxygen while they take up CO2, but when the light goes out, photosynthesis stops and they give off C02 instead. Might not make much difference but it must make some difference. There are people who think you should not sleep in a room with live plants because there's a risk you might suffocate due to their off gassing of CO2.

From what I understand, plants use up more C02 than they ever give off, but in a densely planted tank I would think a measurable change would occur every night, if anyone bothered to measure.

Other parameters in nature can change drastically as well. Heavy rains, whether from sudden storms or seasonal variations, would make for a substantial reduction in TDS, since salts and minerals would be greatly diluted. If the rains also washed large amounts of organic detritus into a body or water, it surely would have an effect on pH, just as leaves, wood or peat do in our tanks. 

Otoh, if there is prolonged drought or seasonal evaporation, TDS would increase as salts and minerals become more concentrated, to the great extreme of actual salt pans in some places water has completely evaporated. Not much lives in such places, but some critters and plants have learned to greatly extend their periods of dormancy to cope with extremes. 

I doubt that there are very many fish or plants that cannot tolerate some degree of change to their living conditions, it's more or less the rhythm of nature. I doubt they'd exist otherwise, because water is always subject to being affected by what is added to it and by what leaves it, via evaporation.

I know, tanks are small, closed environments, where smaller changes may have greater effect than they could in lake or river sized bodies of water, but I think the changes from day to night with C02 are likely not worth worry.


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## BillD (Jun 5, 2006)

aniroc said:


> PH fluctuation because of CO2 level is not harmful to fish because TDS is not affected. In fact, any planted tank will have lower pH in the morning, before lights are turned on.
> Its the osmotic pressure fluctuation that stress fish, not pH itself.


Indeed. Regardless, people still perpetuate the "pH shock" myth. The other thing attributed to pH shock is the sudden pH fluctuation you get when you open a fish bag that has traveled for some time. The issue isn't the sudden rise in pH, but rather what happens to the ammonium in the bag when pH rises above 7 and the non toxic ammonium is converted to ammonia, which is toxic.


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