CO2 at night - The Planted Tank Forum
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post #1 of 7 (permalink) Old 02-25-2006, 07:05 PM Thread Starter
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CO2 at night

I've always ran CO2 24-7.
I tried running an air stone the other night to stop the CO2 spike.
The next morning i had very little CO2 and a really high PH.
My question is, can I run a stone at night without losing all my CO2?
Not sure what's better, Really high or really low CO2 levels in the morning.
Seems that I'm inviting Algea or dying fish.
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post #2 of 7 (permalink) Old 02-25-2006, 07:10 PM
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If you have had success running the CO2 24/7 why mess with it?
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post #3 of 7 (permalink) Old 02-25-2006, 08:52 PM
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Originally Posted by Carson
I've always ran CO2 24-7.
I tried running an air stone the other night to stop the CO2 spike.
Don't worry about the decrease in pH at night. Experience has shown that this isn't going to cause any real problems as long as your fish aren't gasping in the morning. It just causes CO2 wastage. One could in fact argue that that it's beneficial in terms of getting your plants photosynthesizing as early as possible during the day and helping keep algae down by keeping the CO2 concentration high.

From what you've said, though, I'm a little suspicious you were providing too much aeration. I've run various amounts of air through my 29g at night, and the effect on pH/CO2 can vary dramatically, all the way from very little effect on pH to a very strong effect on pH (almost purged the tank of CO2!). For fun, why don't you try messing around with different amounts of aeration to see how it works out for you?

Nighttime aeration does have the avantage that it helps keep down surface scum. Also, be aware that relatively little aeration is required to raise the dissolved oxygen concentration if you aerate all night long.

Lastly, a final possibility is to increase your KH to provide better buffering and thereby reduce the magnitude of the pH swing during aeration. It will also allow you to put more CO2 in at a given pH. It's also overkill. What Rex said applies if you just want to maintain your tank with minimum fuss.
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post #4 of 7 (permalink) Old 02-25-2006, 10:14 PM
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if you're concerned about the CO2 spike, why not just spend $20-30 on a solenoid? you can do the simple math to determine how long it would take to get back the return on your investment. if you assume the cost to refill your tank is about $10-15 and you're using twice as much CO2 as you need to ...
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post #5 of 7 (permalink) Old 02-26-2006, 12:28 AM
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If your only goal is to limit the CO2 Spike at night I second the solenoid. Just put it on the same timer as the lights. Yeah Co2 levels will be a little low for a few hours in the morning, but it's nothing to worry about since the plants won't be using much Co2 while they are waking up.
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post #6 of 7 (permalink) Old 02-26-2006, 12:58 AM
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Adding CO2 only during the day lets you add more/at a higher rate during the day.....when you actually need CO2, so the time to get it up high is rapid, Should be less than 1 hour.

We do not need to add CO2 at night, the pH issue....never was an issue, we add CO2 for plants, not to control pH.

Adding CO2 only during the day allows the plant tank to gas out any excess build up CO2 each night. Fish don't like high CO2 all night either, when the CO2 is high, so is the O2.

Tom Barr

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post #7 of 7 (permalink) Old 02-26-2006, 03:09 AM
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i just run CO2 24/7, i slowly adjusted it so I would get ~30 ppm of CO2 according to the KH/pH table. Then I just adjusted the filter outake tube so I got enough rippling to keep the fish happy but not too much to lose the CO2. Once you get the setup right you don't need to adjust it.
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