CO2 question.... - The Planted Tank Forum
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post #1 of 9 (permalink) Old 11-06-2003, 08:56 AM Thread Starter
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Do you think its better to just turn off CO2 with the lights or do you think its better with the ph monitor/controller combo
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post #2 of 9 (permalink) Old 11-06-2003, 11:55 AM
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It depends, and I'm assuming we are talking about a pressurized system:

How fast are you pumping the CO2 in;
How big is the aquarium;
Do you have any filters mixing the water at night;
Do the filters ripple the surface water;
What is the bioload of the tank (fish and plants);
How hard is your water;

I don't turn mine off at night on my 30 gallon tanks, but I am not pushing in excessive amounts. My fish bioload is light and the plant bioload is stupidly high, yes extensive thinning is needed. I have power heads mixing the water column while trying to avoid surface ripples. Water is not real hard out of the tap, but I do add Calcium to try to raise it up a little. I never see stressed fish in the morning so I am not worrying about it.


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post #3 of 9 (permalink) Old 11-06-2003, 12:09 PM
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If you got the choice between no monitor/controller or with monitor/controller, go with the controller. I don't like the idea of switching off CO2 at night. When I didn't have a controller I always left the co2 on 24/7. This is my opinion and others may disagree but I see no need to turn off the CO2 at night.

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post #4 of 9 (permalink) Old 11-06-2003, 03:21 PM
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I'd either do a full-blown pH controller and solenoid, or just leave it on 24/7, the way I do. The only way I'd really demand a pH controller is in soft water, without good buffering capacity, or with delicate fish such as Discus.

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post #5 of 9 (permalink) Old 11-07-2003, 10:07 PM
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Have to agree that with a pressurised system you do not need to turn off the CO2 at night.

Turning off can create unstable Ph swings. The Ph will rise if you have surface agitation. With no CO2 to counter the rise, Ph can rise sufficiently to cause a problem.

Anyway just my experience

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post #6 of 9 (permalink) Old 11-14-2003, 10:12 PM
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Hi everyone, I am newbie here. But as far as I know that during the night the plant is releasing CO2 and if we leave the CO2 running during the night, I think it would create a lot of problem such as lack of O2 (in a heavy planted tank) and PH drop. As a result all of the fishes in the tank would be suffering.

Please correct me if I am wrong.
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post #7 of 9 (permalink) Old 11-15-2003, 02:07 AM
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The addition of C02 in an aqaurium doesnt nececarily replace the amount of 02. Plus plants will produce 02 as a result of the C02 fertilization. Raising kH could prevent or minimize acid drop.
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post #8 of 9 (permalink) Old 11-15-2003, 02:17 AM
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Yes, you are correct about fish and plants both releasing CO2 at night and that there is a possibility of a lack of oxygen in the tank......but only in a heavily stocked tank. I have about 25 - 30ppm CO2 running all day in my 55 gallon, and I don't turn it off at night. I check on the fish in the morning for a while after fiddling with CO2 regulator/needle valve, and have seen no problems or stress in the mornings. I do have a decent amount of surface movement, although not agitated surface. A slight ripple is the most that happens, even when the water gets real low. I have a LOW fish population, by any standards, and PLENTY of plants. I actually have at least 90% of the substrate covered (no joke), since I'm trying to get my tank established and stop algae from taking over.

As far as all that CO2 driving out the oxygen, this isn't what's actually happening. While O2 being pumped into the water does gass off CO2, the reverse doesn't happen. The fish/plants utilizing O2 without the plants reproducing more O2 is why the fish run low on oxygen. This is why most credible aquarium plant setup guides state to lightly or moderately stock the tank for best results. It also has a big factor with algae growth.

I'm a firm believer that if you are not using a CO2 controller, then you should leave your CO2 running all night. If you are having problems in the morning, I'd add an airstone and small air pump and set it on a timer to come on at night. Better yet, I might even try having it run for a period of time, then turn off for an hour, then run, turn off, etc. I'd fiddle until I got things balanced. I'd also cut the air pump off about an hour ( or maybe 1/2 hour) before the lights come on to build up some CO2 for early photosynthesis.
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post #9 of 9 (permalink) Old 11-15-2003, 01:54 PM
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Sumpin'fishy, I think your idea is very good indeed. I might give it a go one day :lol:
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