# Turning off CO2 at night



## PuddlesAqua (Jan 5, 2013)

I have a small CO2 rig I just set up. Paintball canister with an ASA on/off, pressure gauge and needle valve, attached to a check valve, bubble counter, and diffuser. I want to turn the CO2 off at night to maintain a stable pH for my shrimp. Can I just turn off the CO2 via the ASA on/off and then turn it on in the morning? I wouldn't need to mess with the needle valve right?


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## funnytrash (Sep 5, 2010)

itd be best if you could get a solenoid


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## neilshieh (Jun 24, 2010)

yes you can turn your paintball co2 off via the on and off knob. 
using a solenoid probably won't work because with paintball setups the pressure isn't regulated so unless you can find a solenoid that can handle atleast 800psi then that will not be an option. needle valves doesn't need to be adjusted.


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## ryantube (Aug 9, 2011)

Any idea how to turn of yeast CO2?


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## OTPT (Sep 27, 2010)

ryantube said:


> Any idea how to turn of yeast CO2?


Ah, I had thought about that before I've got a pressurized system.
I thought about using a 3 way splitter with one output to the tank.
And another one to a solenoid that would close when turning on (forcing CO2 to flow 
through the first route, into the tank), and open when turning off
(to release CO2 to the atmosphere at night). Because CO2 gas will flow 
through the path with the least resistance.

I prefer the use of normally open solenoid here because the service life will 
probably be longer from shorter operating hours (less accumulated heat to the coil).


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## farrenator (Dec 21, 2008)

PuddlesAqua said:


> I want to turn the CO2 off at night to maintain a stable pH for my shrimp.


Turning off your CO2 will have the opposite effect. It will cause pH to rise. When CO2 dissolves into water it turns the water more acidic. So turning your CO2 off at night will cause the water pH to rise as the dissolved CO2 offgases.

I know plenty of people keep shrimp (me included - cherries) with CO2 on during the day and off at night - but that is another story. If the only reason you want to turn the CO2 off at night is to keep the pH stable, then don't.


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## Yo-han (Oct 15, 2010)

farrenator said:


> Turning off your CO2 will have the opposite effect. It will cause pH to rise. When CO2 dissolves into water it turns the water more acidic. So turning your CO2 off at night will cause the water pH to rise as the dissolved CO2 offgases.
> 
> I know plenty of people keep shrimp (me included - cherries) with CO2 on during the day and off at night - but that is another story. If the only reason you want to turn the CO2 off at night is to keep the pH stable, then don't.


True! But if your CO2 keeps running and it is not used (at night) than CO2 will increase, thus pH will decrease. Keeping it stable will only be possible with a pH controller IMO. But pH is of no issue, not for fish, not for shrimp, if the pH change comes from CO2 alone. pH shifts from KH shifts are dangerous, from CO2, not problem at all! The pH in my tank shifts from 7.5 to 6.2 (turning CO2 on) in an hour. And after turning CO2 off, it slowly goes back to 7.5, every day!

Still I think turning it off at night is a good idea, especially for the bacteria in your tank...


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## bigred35 (Apr 25, 2012)

i thought about turning mine off at night also.. but have not done so yet.. I am around 2 bubbles a min on a 150 gal tank... it has only been running a week so not sure what changes have taken plac yet. if any


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## MrBones (Feb 23, 2013)

Yo-han said:


> True! But if your CO2 keeps running and it is not used (at night) than CO2 will increase, thus pH will decrease. Keeping it stable will only be possible with a pH controller IMO. But pH is of no issue, not for fish, not for shrimp, if the pH change comes from CO2 alone. pH shifts from KH shifts are dangerous, from CO2, not problem at all! The pH in my tank shifts from 7.5 to 6.2 (turning CO2 on) in an hour. And after turning CO2 off, it slowly goes back to 7.5, every day!
> 
> Still I think turning it off at night is a good idea, especially for the bacteria in your tank...


I have this very same issue. I decided to stop the Co2 altogether and just dose daily with Excel for the Carbon. My KH stays high but my PH is constantly at 7.4-7.6 and I would like it lower, 6.8-7.0. I do have air bubbling in for a few hours at night which I think I will stop for a bit and see if that won't allow the PH to lower but I don't want to wake up to gasping fish either. My kh is at 7dKH and PH is 7.6 right now.


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## TarantulaGuy (Apr 15, 2009)

Yo-han said:


> T But pH is of no issue, not for fish, not for shrimp, if the pH change comes from CO2 alone. pH shifts from KH shifts are dangerous, from CO2, not problem at all!


I'm curious as to why I hear this constantly. If it's changing because of lack of a buffer, or artificially through CO2, shouldn't it have the same effect regardless? Granted, I am not a chemist, but I'd like to know the actual scientific data that backs this statement up.


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## DeeJayA1 (Oct 7, 2011)

PuddlesAqua said:


> I want to turn the CO2 off at night to maintain a stable pH for my shrimp.


Wouldn't that cause a swing in pH when the co2 is turned off??


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## Yo-han (Oct 15, 2010)

Yes... But fish don't notice this although you may read the opposite quite often. Fish notice only a change in pH if it is due to a change in KH, not really if it is done with CO2. Fish don't carry a pH meter. But a change in KH changes the osmotic pressure so they notice this.


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## maxwellag (Jun 1, 2012)

Closing the exit of co2 in a DIY sugar and yeast reactor (when a plastic bottle is used) can make a big mess. The pressure builds up and can cause the bottle to explode.


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## TarantulaGuy (Apr 15, 2009)

Yo-han said:


> Yes... But fish don't notice this although you may read the opposite quite often. Fish notice only a change in pH if it is due to a change in KH, not really if it is done with CO2. Fish don't carry a pH meter. But a change in KH changes the osmotic pressure so they notice this.


So pH would have no effect if this is true, only KH? I acknowledge that fish are generally pretty tolerant of pH swings and variation, but I can't believe that they're totally unaffected by it, even if it isn't accompanied by a KH change as well. Hmm. I need to do some digging in the literature.


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## Yo-han (Oct 15, 2010)

Off course they notice pH 3-8 difference if done with acids, but I think it is more like us. We can feel and taste the difference between very hard and very soft water. Fish are much more able off course. But when I adjust the pH by 1 only with an acid (CO2 in this case) you won't notice and the fish probably neither. If I add enough HCl to drop it below 3 maybe you can, fish a little sooner maybe. As long as it are no big swings or very fast swings than it will be no problem. 

Fish can adapt more than you think. For example, when it rains in shallow rivers, pH can drop in a few hours as well. As long as your fish are healthy and no extremes are tested, fresh water fish are quite adaptable!


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## Yo-han (Oct 15, 2010)

Off course they notice pH 3-8 difference if done with acids, but I think it is more like us. We can feel and taste the difference between very hard and very soft water. Fish are much more able off course. But when I adjust the pH by 1 only with an acid (CO2 in this case) you won't notice and the fish probably neither. If I add enough HCl to drop it below 3 maybe you can, fish a little sooner maybe. As long as it are no big swings or very fast swings than it will be no problem. 

Fish can adapt more than you think. For example, when it rains in shallow rivers, pH can drop in a few hours as well. As long as your fish are healthy and no extremes are tested, fresh water fish are quite adaptable!


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## tipsy mcstager (Apr 6, 2013)

Yo-han said:


> As long as it are no big swings or very fast swings than it will be no problem.
> Fish can adapt more than you think. For example, when it rains in shallow rivers, pH can drop in a few hours as well. As long as your fish are healthy and no extremes are tested, fresh water fish are quite adaptable!


i agree 100% with that! (except the sad part, why. acid rain!)

with 8.0 kh/ 7.6 PH out of my tap, my tank PH will change to aroud 6.8 in the first hour of it (CO2)being *on, and peek to 6.6 in about 2 1/2 3 hrs. till the timer shuts the CO2 *off.
and not to forget, increased surface agitation will make for better gas exchange of O2 and C02.

*i don't turn the C02 off on that tank anymore, when the C02 go's off. a power head kicks on and i'll see a PH change to 7.0-7.2 within 2 hrs.................and that works well for me:der:


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## rhodophyta (Jan 23, 2006)

The rationale for turning off CO2 at night is still sometimes in the belief that plants don't absorb CO2 in the dark. Some plants absorb CO2 ONLY in the dark because they are from hot climates and there is an energy cost to absorbing CO2 during the hotter daylight hours. The rest of the plant life absorbs CO2 24/7. 

Don't get me wrong. I am not saying that you don't have a reason to turn off CO2 at night. You may well have reasons, but blaming it on plants is not right. Some years ago an individual campaigned that house plants were responsible for SIDS, sudden infant death syndrome. This person distributed a lot of misinformation that plants absorbed oxygen and exuded CO2 at night, asphyxiating infants and pets.


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## Lusher (Apr 19, 2013)

mine got a diy co2 system sugar and yeast never turn them off. my fish are still fine.


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