# Aeration in regard to CO2?



## Bob-O (Jan 28, 2012)

So in my heavily planted 90 gallon tank, I'm running an airstone whenever the lights are on unless I have dinner guests. Tank is in the dining room and the fusion air pump can be rather loud (Side question is there a silent one?). I'm currently trying to get micro sword to spread out on the bottom and a java fern to spread on a rock. The inverts in the tank (shrimp and snails) seem to enjoy the aeration and I like that it keeps the water moving.

Short version, will NOT running the airstone make a significant difference on CO2 levels since since gas exchange would be lower? Or am I over thinking this?

Running two eheim canister filters, so while they create a bit of a current, they don't cause much surface agitation, and IMHO don't contribute much to gas exchange.

Thanks in advance. I love this forum.


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## jrman83 (Jul 9, 2010)

I wouldn't worry about CO2, unless you are injecting it. Running an airstone will generally cause CO2 to gas out of the water. Lack of surface water movement maybe more so. Either way if your plants are doing fine I wouldn't worry about it. None of the plants you mention are difficult or have higher demands. If you want more surface movement, add a powerhead or aim the spraybars upward.


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## Auban (Aug 8, 2010)

Without injecting co2, running an airstone keeps co2 levels in equillibrium with atmospheric levels. Without light(night time) plants produce co2 and use o2, so at night aeration lowers co2 levels in the tank. During lighted hours though, plants use co2 quickly, so aeration maintains co2 levels at atmospheric levels, which are higher than they would be after just a couple of hours of photosynthetic activity. In otherwords, without injecting, aeration is beneficial to plants. With co2 injection, however, its wasteful.


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## coralbandit (Jul 29, 2012)

if plants are growing well , most tanks lack co2.(not beginners, but succesfultanks) , the intro to oxygen is best applied at nght. Plants eat oxygen at night(reefers have to wait till daylights have taken effect before attempting ph reading) and eat co2 during photo you know. Just say no to oxygen during day. Am I all wrong ?


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## Auban (Aug 8, 2010)

coralbandit said:


> if plants are growing well , most tanks lack co2.(not beginners, but succesfultanks) , the intro to oxygen is best applied at nght. Plants eat oxygen at night(reefers have to wait till daylights have taken effect before attempting ph reading) and eat co2 during photo you know. Just say no to oxygen during day. Am I all wrong ?


plants typicaly spend the day producing sugar through photosynthesis that gets stored in the cells. at night, they use the stored energy produced during the day for cell devision. during the night they indeed need oxygen. on the same note, you are also correct in saying that there isnt much CO2 in a tank during the day, since the plants typically use it up. this brings us to the topic of aeration, using atmospheric air(standard aquarium air pump). during the day, a heavily planted tank will use up CO2 very quickly. surface agitation and aeration can maintain CO2 closer to the equillibrium with atmospheric levels. this means that it really all depends on how much plant matter is pulling CO2 from the water. if there are only a couple small plants, then it wont make much of a difference, since a circulated tank will likely never run out of CO2. however, in heavily planted tanks like mine, circulation and agitation are a benefit. i use it at night to keep the O2 levels from getting too low and during the day to keep the CO2 levels from getting too low, but this is only during the times i am not injecting CO2. the absolute best way to go about it would be to add aeration during the night and inject CO2 during the day. if you cannot do this, it is usually better overall to keep aeration going at all times. 

one caveate to this is the that some believe that plants may benefit from the early morning surplus of CO2. this would mean that you may want to turn aeration off at night to let the CO2 levels build, and wait untill a few hours after you turn the lights on to start aeration, giving the plants time to use up the CO2 that built up the night before. in my experience, it made no difference to the plants but did seem to bother the fish. every morning the fish were up gasping for air, and the plants didnt seem to grow any faster than if i used continuous aeration(without injecting)


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## Auban (Aug 8, 2010)

Bob-O said:


> Running two eheim canister filters, so while they create a bit of a current, they don't cause much surface agitation, and IMHO don't contribute much to gas exchange.


if the water is able to flow from the surface to the bottom and back all night long, it is likely promoting enough gas exchange to keep O2 levels up. i would say you should keep doing what you are doing. as long as nothing seems to be suffering, stick with what works.


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## Bob-O (Jan 28, 2012)

Thanks for all the prompt responses. As with most things, I believe I was over thinking this. =P I think I'm going to just keep aeration going at all times and maybe try a few hours off when the lights turn on. Although I was checking out some of the DIY CO2 setups. They seem fairly simple and cheap, so I'm thinking it would be a good way to try a CO2 system before I invest a bunch of dough into one. I'm not opposed to a CO2 system, but I've kept it pretty simple so far and I've had great results. For someone with a planted tank and a kitchen garden, you'd think I would have more patience when it came to plant growth. =) Thanks again.


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## beaslbob (May 29, 2009)

While plants consume co2 and produce o2 with lights on.

and

use o2 and produce co2 lights off


the overall effect is to make the tank a net consumer of co2 and producer of o2 during each 24 hour period.

It could be possible that circualtion/airation with their increased air/water interchange would actually lower o2 and increase co2 in a heavily planted tank as compared with no circulation.

my .02


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## jrman83 (Jul 9, 2010)

beaslbob said:


> It could be possible that circualtion/airation with their increased air/water interchange would actually lower o2 and increase co2 in a heavily planted tank as compared with no circulation.


Not possible. Air/water exchange is the most effective way to get oxygen in a tank. Plants alone are not as effective in performing this function. This info can be found in numerous articles on the web and in more of your notable books like Walstad's. 

So how would one increase while the other decreases? The tank will intake both simultaneously through the water's interaction with the air above it. Since CO2 is about .04% globally, it would not displace the other.

In a no circulation/water movement tank, this exchange has difficulty in occuring making the tank lower in oxygen even with plants, as compared to a planted with circulation and water movement. Plants consume what CO2 is there, but likely wouldn't get the amount they need to be healthy. Alive and growing maybe, but healthy - not compared to one with a little more CO2 to consume.


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## OaklandFISH (Aug 13, 2013)

If I am going to be injecting co2 using the Hagen Nutrafin CO2 Natural Plant System with CO2 Activator and Stabilizer ( this runs constantly) is it correct that when the lights are on during the day I should stop airation (I have a bubble wand) and at night when the lights are off turn airation on so that there is not too much co2 between the plants natural process at night and the co2 injection system running?


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