# Confusion with using CO2 at night.



## Melissa3 (Feb 27, 2007)

I'm going to be setting up pressurized Co2, with a DIY reactor. I've read that CO2 should be turned off at night because plants don't use it and they use oxygen instead. I also read that CO2 has an effect on pH and the more CO2 in the tank the lower the pH level. 

I'm still new at this, so please bare with me  , but I'm guessing that turning the CO2 off at night would result in the pH level going up and then turning on again in the morning would result in pH going down?

I'm wondering, is there a huge effect on the water parameters if you keep turning the CO2 on and off? Also, is the effect enough to be potentially harmful to fish?


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## Squawkbert (Jan 3, 2007)

What we have here is failure to communicate. -Strother Martin

DIY CO2 - yeast, sugar, water pumping CO2 at modest pressures into tank - your bottle or some kit - doesn't matter, we generally call anything w/ yeast a DIY.

Pressurized CO2 - a steel or Al tank containing CO2 at a pressure of 2000-3000PSI.

If you have DIY, don't sweat shutting it off at night. Doing so is likely to cause problems and won't fix any.

If you have pressurized, and you have a solenoid valve on your regulator, it's easy to plug the solenoid valve into a timer and shut the tank off during the dark cycle. If you don't have a solenoid valve, I wouldn't bother as long as your CO2 flow maintains a constant 30ppm or less of CO2 during the light cycle. If you are maintaining higher levels of CO2, you may want to shut it off at night, or hook an air pump up to a timer and run it at night, but that will not prevent serious problems in the event of a power outage at night if you're pumping too much CO2 into the water.

The advantage of having a solenoid is that your CO2 tanks will last longer. Plants won't suffer as they don't use CO2 when it's dark. Putting a solenoid on a DIY won't really make the system last longer as the yeast will keep producing CO2 whether there's light or not, whether the solenoid is open or not... you'd just get a big burp of CO2 in the AM from the added pressure, most of the excess CO2 would probably find its way into the air anyway.


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## Muirner (Jan 9, 2007)

Wait squawk- your saying that my CO2 bottle should have been filed to 2000PSI? Mine on initial hookup was under 1000PSI. I'm using a brand new 5lb aluminum cylinder. I thought that CO2 was filled at a much lower psi then most.


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## eklikewhoa (Jul 24, 2006)

Mine was only filled to about 1000psi as well...and it's been sitting at 900 for the past few months.

Back to the question though.... co2 is not used at night bu can not do any harm if you are not pumping it into the tank and an insane amount. If you water/tank is able to buffer (kh) it the swings will not be great and should stabilize. I have different tank which some are on 24/7 and others on a timer and have to say that the one that is on 24/7 is more stable then the other. My KH keeps the ph stable so there aren't and crashes or swings and with it on all time it is also consistent.


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## Melissa3 (Feb 27, 2007)

I apologize for the confusion on my part.  I was _originally_ going to go with DIY yeast, until I heard about shutting the CO2 off at night. The only DIY part now would be the diffuser I plan to make.

I think I understand the concept now. I just thought that if I left the CO2 on at night it would cause an overdose, since the plants wouldn't be using it, and that my fish would die. But I don't plan on using a huge amount of CO2 since the tank is only 10gal.

Thanks for the info


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## eklikewhoa (Jul 24, 2006)

You can't technically turn off DIY so no need to worry.


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## Left C (Jun 14, 2005)

Melissa3 said:


> ...I've read that CO2 should be turned off at night because plants don't use it and they use oxygen instead...


I just want to mention an often seen misconception about plants. Plants use O2 24/7 for cellular respiration just like almost every living organism.


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## MTechnik (Feb 17, 2005)

CO2 liquifies past 8-900psi.

-MT


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## snickle (Apr 8, 2007)

My take is this:

If you are going DIY CO2 (Yeast based), you are going to have a hard time over injecting and shutting off at night would cause way more problems than it solves.

If you are doing presurized CO2, than if you are maintaining at 30ppm during the day, then you need to shut off at night.

If you are maintaining at 15ppm then you should keep it running to minimize the chemistry changes in the tank.


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## eklikewhoa (Jul 24, 2006)

My Mini tank has pressurized and it's about 30ppm which stays on 24/7. No gasping fish and the shrimp don't seem to be effected at all.


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