# Simple CO2 question



## tungsram (Mar 1, 2005)

I have succesfully completed a DIY CO2/powered reactor setup. I'm getting great production and everything was a lot easier than I had imagined, however... how do I "turn it off" at night? Simply unplug the air line, or should turning off the powerhead be sufficient?

I searched for an answer but got like 50 pages of results so forgive me if this question has been asked before.


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## Damon (Jan 18, 2005)

You shouldn't have to turn it off at night with a DIY setup. Most dont turn them off even with a CO2 cylinder and powered reactor. If you wanted to though I would unplug the airline and turn off the powerhead.


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## tungsram (Mar 1, 2005)

Well, as you know there is a lot of varying information about any topic floating around the Internet. There is no photosynthesis in the absence of light, so there is nothing to leech the CO2 out of the water at night- CO2 being toxic to fish in high levels. You see where my line of thought was heading?

But if the general rule of thumb is to leave it "running" then I'll give it a shot. I should know pretty quick if it was a bad idea or not.

I guess I'm thinking too much about this. CO2 is heavier than "air" so if I leave it running at night it seems like the bubbles traveling to the surface would form a gaseous layer on the top of the water which would keep air from contacting it. I do no use any external O2/air pumps, so much of the O2 in the tank comes from the plants and that from the surface of the tank. No photosynthesis = no CO2 removal and no O2 production which in _theory_ = dead fish.

I'll walk away quietly now...


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## Damon (Jan 18, 2005)

lol.  Its not an absurd line of thinking.
Here is a link to another site with a topic on such.  Pay special attention to Jeff Senske's (jsenske) and Tom Barr's (plantbrain) posts.  Good info but dedicated to pressurized co2 vs. DIY.
http://www.aquaticplantcentral.com/...?t=4987&page=2&pp=10&highlight=turn+CO2+night


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## DavidDoyle (Jan 18, 2005)

To know if you really need to "turn it off" check your pH a few hours after lights out and then right before lights on. If you are not getting a noticable pH drop, then you are fine.

Rather than turning it off and on, it is easier to use an airstone with the pump on a timer. The airstone should go on at lights off and turn off about 30 minutes before lights on. The airstone will outgas the co2 via surface aggitation.


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## tungsram (Mar 1, 2005)

Actually I did that and it dropped .8 from lights off to on. The fish didn't seem bothered, I guess I was more worried about long term effects. I mean we can swig two or three beers a day with little impact on our health, but when done for 12 years straight, it can really "poison" you.


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## Fla280zxDrifter (Mar 27, 2005)

turning it off will cause a flucuation in the Ph, among other things. . . someone probably already mentioned this but, i didn't feel like reading all of it


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