# CO2 at night



## reefteach (Sep 26, 2004)

Should CO2 solenoids be controlled with a timer, so it goes off the same as the lights? I have seen a little of positive, and a little of negative on this. This would be a cheap way pf avoiding the pH controller.


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## elTwitcho (Jun 22, 2004)

yes it should. That is the ideal method of doing things, but any way will work so long as you stop injecting once the lights go out.


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## l2ob (May 22, 2004)

how can u control the selenoids? like where/what do u get


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## elTwitcho (Jun 22, 2004)

l2ob said:


> how can u control the selenoids? like where/what do u get
> [snapback]936476[/snapback]​


A solenoid is an electronic valve. You put it on a timer and it shuts off the flow of CO2. This only works in pressurized systems, it does not work on yeast CO2 systems.


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## reefteach (Sep 26, 2004)

I was thinking about getting this system. I know that there are lots of DIY solutions, but the time/effort in my case would lead towards a set system like this that is already set.

http://www.drsfostersmith.com/product/prod...935&N=2004+2021

As far as the solenoid question, you can either hook it up to a timer like this system, or spend another $80 and get a pH monitor which will turnit on and off based on pH. The pH can be considered an indirect measure of CO2.

Thanks for the advice.


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## Raul-7 (Sep 1, 2004)

Many people in the planted tank hobby run them 24/7 without any problems. Turning C02 off at night can cause unwanted pH swings that stress-out your fish. But running 24/7 can also cause your pH to crash if you have a low buffering capacity.


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## elTwitcho (Jun 22, 2004)

Generally, most people turn their solenoids off at night, that's why every complete kit comes with a solenoid in the first place. Turning them off will cause a gradual change of .4 - .6 which over the course of an entire night is not a big deal. The plants are releasing CO2, and the breaking down of waste is releasing CO2, and it takes a while for it to difuse out of the water, it's a very gradual process that won't have an effect on your fish.

Leaving it on however, is much more likely to cause your ph levels to crash. You might think it's the more stable of the two but that's not at all true. Yes you're still injecting the same amount of CO2, but that CO2 is no longer being used by your plants and is only leaving the tank by difusion at the surface. Combined with the plants producing CO2 and the other biological processes in the tank, and you're much more likely to see instability by continuing to add CO2 than if you turned it off.

I personally haven't heard of more than a couple people who run their CO2 all night, aside from the risks of instability, it's a waste of CO2 and your bottle will only last half as long between charges.


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## DonH (Jan 25, 2003)

When I had a planted tank, the CO2 turned off when the lights went off and an airpump was timed to turn on shortly afterwards. It worked too well... I tore down the tank because it was too much work trimming all the plants back.


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## reefteach (Sep 26, 2004)

DonH said:


> When I had a planted tank, the CO2 turned off when the lights went off and an airpump was timed to turn on shortly afterwards. It worked too well... I tore down the tank because it was too much work trimming all the plants back.
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> ...


Why turn the air pump on at night? I have two air pumps now in my 150g. Just started putting plants in . When I upgrade to better lights and co2, I should get rid of the pumps, or so I have been told. But having them at night seemed to work pretty well for you. Curious as to why.


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## DonH (Jan 25, 2003)

Plants take in dissolved oxygen at night and release carbon dioxide. Therefore, having an airpump to aerate the water will degas carbon dioxide and help maintain dissolved oxygen for both plants and fish.


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## reefteach (Sep 26, 2004)

DonH said:


> Plants take in dissolved oxygen at night and release carbon dioxide. Therefore, having an airpump to aerate the water will degas carbon dioxide and help maintain dissolved oxygen for both plants and fish.
> [snapback]937915[/snapback]​


thanks!


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## Husky_Jim (May 26, 2003)

I personally prefer a solenoid attached to a PH meter and not just turning the Co2 off at night ......(eventhough i have used this method in the past)


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