# CO2 running 24/7



## Victor (21 Mar 2021)

Hi there. It's a good idea to run CO2 24 hours a day? I'm asking because I recently began to inject CO2 24/7 to eliminate ph swings in my tank. I know ph swings are harmless to fishes but I have crystal red shrimps. For sensitive shrimps like that I think ph swings of more than 1 ph unit in less than one hour (typical from CO2 injection during photoperiod) can be harmful. So running CO2 24/7 my ph swings from 6,4 to 6,3 with 1 dkh (about 20 ppm of CO2). There are something to being concerned about this approach? Thank you.


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## noodlesuk (21 Mar 2021)

I've not heard this being done before is it worth investigating the cause of the pH change instead? Or are you saying the swing is from the CO2, so keeping it on all the time stops this? Does it change with photperiod?


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## Zeus. (21 Mar 2021)

Many folk have had success with CO2 on 24/7, they do tend to use lower CO2 levels ( a few BPS). I would increase the dkH to 2dkH for a little more stability.  Adding 3.57grams of Potassium Bicarbonate to 100l of tank water will raise the dKH by  1.0, or just toss a level teaspoon in per 100litres and call it good.


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## Victor (22 Mar 2021)

noodlesuk said:


> I've not heard this being done before is it worth investigating the cause of the pH change instead? Or are you saying the swing is from the CO2, so keeping it on all the time stops this? Does it change with photperiod?


Yes, the ph swing I was experiencing before was due the CO2 injection at photoperiod (10 hour a day). The ph was swinging a whole unit (1,0 ph) in just 1 hour. So to solve this problem I set the CO2 running 24/7 to eliminate that ph swing. This way my ph swing now is just 0,1 unit a day (from 6,4 to 6,3 instead a whole unit as seen before).


Zeus. said:


> Many folk have had success with CO2 on 24/7, they do tend to use lower CO2 levels ( a few BPS). I would increase the dkH to 2dkH for a little more stability.  Adding 3.57grams of Potassium Bicarbonate to 100l of tank water will raise the dKH by  1.0, or just toss a level teaspoon in per 100litres and call it good.


Actually I have a very good surface agitation so I need to keep a high BPS rate to maintain CO2 stable at 20 ppm.  I think it's not a good idea to increase the kh because crystal red shrimps don't like it. They prefer kh nearly 0 (about 0,3 dkh). In my case, the only reason to keep CO2 24/7 is to ensure stable ph for CRS.


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## Victor (22 Mar 2021)

I was thinking to drop the kh even more to 0,3 degree but at this level the ph would be stable at 5,7 with CO2 24/7. This is too acid to nitrifying bacteria survive, isn't it?


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## Zeus. (22 Mar 2021)

Victor said:


> I was thinking to drop the kh even more to 0,3 degree but at this level the ph would be stable at 5,7 with CO2 24/7. This is too acid to nitrifying bacteria survive, isn't it?


Reducing the kH may potentially make injecting CO2 and getting a stable pH tricky, proceeded with cation. Never had CRS due to having very hard water.


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## Mark Nicholls (23 Mar 2021)

There WILL be a pH swing in a heavily planted tank whether or not CO2 is infused. 
Here's why:
CO2 is acidic
O2 is alkaline. 
Plants photsynthesise producing oxygen during the day but they BREATHE producing CO2 24hrs a day. This means that during a 24hr period there are slight net swings in pH. PH will drop at night. Therefore, if your CO2 is running 24/7 it's a good idea to aerate the water during the night.


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## JoshP12 (23 Mar 2021)

Victor said:


> I was thinking to drop the kh even more to 0,3 degree but at this level the ph would be stable at 5,7 with CO2 24/7. This is too acid to nitrifying bacteria survive, isn't it?


You are playing a balancing act. There is no doubt that bacterial activity decreases further away from pH 7. https://www.epa.gov/sites/production/files/2015-09/documents/nitrification_1.pdf

But we need to question why. Enzymatic activity of things like Rubisco also doesn’t do as well at low 6s compared to 7 and 8. The Effect of PH on the Rate of Photosynthesis

So why don’t we build a system to favor this?  I’ve tried. It would have to mimic naturally entirely. Temp swings. pH swings up during the photoperiod - I’ve gone as far as run co2 only at night to favor Rubisco activity during the day. But you have to find a magical amount and that balance requires emotionally connecting with your aquarium in terms of fertilization, observation, pH fluctuations, temperature swings to force metabolism to skyrocket at those higher pHs - favouring bacterial activity ... fueling co2 ... fighting the urge to let that pH go up.

we are missing billions of years of evolution in our dirt. So we would need to lard so much co2 into the sacks of the tank and run enough light and temps to make enough sugar to fuel respiration at night. All this at the cost of potentially throwing the tank off balance.

the balance of what? The balance indicated by a feeing we get when we look at our tanks ... if we are happy, if is balanced.

why does co2 inject during lights on work?  Because it’s a game of economics. Sure bacteria doesn’t work as well - but they still work. What works better? Lower KH. Better carbon assimilation at leaf interface? Soft water fish may favor the environment. Perhaps shrimp?

the larger picture is determine what is it that you are catering to in your tank. And will that cater destroy everything else so much so that you are unhappy - not the forum ... no one cares about what I think about your tank.

24/7 inject of course will work. It means that you have maximum capacity to your injection rate in those plants sacks at lights on and the pH is at this “level” that is sound for everything.

is pH stability that important? Why? Enzymatic function? Bacteria? If so, we know that at some point pH should be higher to favor those ... along with temperature. But then you have to futz around with another timer? Keep it simple. It’s a trade off.

Try things . No one is an authority over your hobby. 

Josh


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