Aerating while injecting CO2. - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 09-25-2015, 02:28 AM Thread Starter
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Aerating while injecting CO2.

I have a 2.5g tank that I'd like to start injecting CO2 in. I have a paintball style setup ready to go with aquatek mini regulator. I also use a submersed filter and aerate my tank with an airstone. I wanted to keep aeration and filtration separate so I could have one or the other at a given time. With the lighting off, the solenoid would cut off the CO2 and the airstone would provide oxygen. My question is, should I leave the air pump on during the period that the lights are on?

There seems to be a couple different schools of thought on this.

Some people say that the surface disruption of an airstone causes an exchange of gas where CO2 leaves the water into the atmosphere and is therefor wasted. If this is indeed true, is it a negligible amount that is lost? I'm using a pretty moderate setting on my air pump, which is a small unit to begin with, so I wonder if it's a non-issue.

Other folks say that CO2 and O2 do not displace one another in water except at very high levels. In that case, it's a non-issue without a second thought.

Now, there is a pretty heavy "bioload" on the tank due to the use of Ramshorn snails which proliferate quickly. I manage them but I tend to keep the tank a hair overpopulated. What total effect that has on dissolved oxygen I'm not 100% sure of but I suspect they use the bulk of it. That is why I want to run the airstone despite plants naturally giving off O2.

I hope I'm not retreading an old topic too much but I just keep tossing this around in my head and it's keeping me from hooking up the CO2 injection altogether. I would also have to build a relay box that would cut power when the relay is powered on(via timer plug) so I could turn the air pump off during the day. I've already started building this box but I'll just set it aside for another aquarium project if it's unneeded.

-mootay
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post #2 of 6 (permalink) Old 09-25-2015, 05:04 AM
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All math points towards surface agitation and the exchange of O2 and CO2. So yes, having an airstone is rather mute and in my opinion will gas off most of your CO2. I wouldn't honestly run one at night either. If you're heavily planted, which I assume you are, hence why you're injecting CO2, your plants are putting off enough oxygen to keep the fish breathing at night, plus with your surface agitation from your filter is enough to make the exchange.

I would never run an airstone in a tank I injected with CO2.
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post #3 of 6 (permalink) Old 09-25-2015, 05:36 AM
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Bottom line is, if your livestock are gasping for air, then they need air.

give off o2 during photosynthesis, but still depends on plant density if they are indeed giving off enough o2 to last during the night. So again, see how the livestock are doing just before the lights turn on for the day (time of least amount of o2, since plants would also be using it and not producing it).

Do you have a filter on the tank? What type? I would think that should be able to provide enough o2 by itself in such a small tank.
People say ripples in water surface is enough, just don't have the water surface break/splash (breaking water surface allowing co2 to off gas).
For that effect, I would think a power head would do a better job creating surface ripples, while air stone bubbles would produce too much surface break/splashing (if you had to do air stone, use fine bubbles as they don't break the water surface/off gas as much)

What livestock are you keeping? If I'm not mistaken, I think snails can go to the water surface and breathe oxygen from the air, I've had bladder snails and ramshorn snails in a bucket of stagnant water and they are still alive and breeding.
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post #4 of 6 (permalink) Old 09-25-2015, 06:52 AM Thread Starter
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Quote:
Originally Posted by WaterLife View Post
Do you have a filter on the tank? What type?
As I mentioned, I have a submersed filter. There is no surface agitation from the filter at all.

Quote:
What livestock are you keeping? If I'm not mistaken, I think snails can go to the water surface and breathe oxygen from the air, I've had bladder snails and ramshorn snails in a bucket of stagnant water and they are still alive and breeding.
At this stage I've moved all of my fish out of the tank and only snails remain. There are Ramshorn and Assassin snails. Both are fairly hardy so it would be hard to gauge what it's like in there for fish, which I hope to be adding back later.

-mootay
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post #5 of 6 (permalink) Old 09-25-2015, 07:42 AM
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I'd put the airstone at a low setting then. Just enough to cause agitation. Nothing huge though. If it does end up being a gasping issue then I'd turn down the co2 before I turned up the aeration.
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post #6 of 6 (permalink) Old 09-25-2015, 10:57 AM
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Quote:
Originally Posted by WickedOdie View Post
All math points towards surface agitation and the exchange of O2 and CO2. So yes, having an airstone is rather mute and in my opinion will gas off most of your CO2. I wouldn't honestly run one at night either. If you're heavily planted, which I assume you are, hence why you're injecting CO2, your plants are putting off enough oxygen to keep the fish breathing at night, plus with your surface agitation from your filter is enough to make the exchange.

I would never run an airstone in a tank I injected with CO2.
Plants give off oxygen during photosynthesis. So, when there is no light to drive photosynthesis, no oxygen.

Photosynthesis creates starches that are stored for later use. This starch is broken down into sugars and converted to energy. This process uses oxygen and releases CO2 and is not light-dependant. So it continues during the night.

Typically, plants produce more O2 than CO2 in a given 24 hr. period. However, O2 gets used by fish, bacteria, and plants. At night, O2 levels can drop very low in a heavily planted tank.

During periods of darkness, aeration is recommended and CO2 injection is not very useful.

During daylight hours, aeration should be reduced or eliminated if there is sufficient surface agitation, surface area, and plants producing O2 to support bacteria and animal life.

Last edited by Argus; 09-25-2015 at 11:03 AM. Reason: spelling correction
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