# How do airstones affect plant growth?



## BBradbury (Nov 8, 2010)

*Airstones*



cjyhc4 said:


> Will the extra O2 in the water help or hinder plant growth? Right now, it seems that all of my critters (fish & shrimp) seem happier with the extra O2. How will this affect plant growth?


Hello cj...

If you use several airstones in the tank, all the bubbles stir up the water surface and mix oxygen and water and release carbon dioxide. Oxygen is a plant waste product, so a high oxygen environment isn't ideal for good plant growth.

Pretty simple.

B


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## Jeffww (Aug 6, 2010)

BBradbury said:


> Hello cj...
> 
> If you use several airstones in the tank, all the bubbles stir up the water surface and mix oxygen and water and release carbon dioxide. Oxygen is a plant waste product, so a high oxygen environment isn't ideal for good plant growth.
> 
> ...



Plants use oxygen just as much as they need CO2.....


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## cjyhc4 (Dec 18, 2006)

B,

Forgive me for not finding your reply particularly simple. Questions:

How does H2O + O2 yield CO2? Or are you saying that the movement of the bubbles forces the CO2 out of the water?

Is this still a bad thing, if there is more CO2 produced than the plants can consume?


Everyone:

I have a single airstone in each tank, regulated according to size, clearly. Just enough to where the inhabitants stop acting stressed. The plants aren't fully adjusted, so the tanks aren't completely stable yet. Still in that initial re-balance stage with die-off, bacteria adjustment, inhabitant adjustment, etc. It's definitely not a HIGH O2 environment. Just adding enough to keep the fish/shrimp content.


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## Jeffww (Aug 6, 2010)

When plants photosynthesize they consume CO2 and produce O2 after stripping water of its hydrogens. However *they will still consume O2 and produce CO2* from cellular respiration *simultaneously.* 

If you aren't adding CO2 to the tank through injection there is no risk to the plant's health, only benefits from increased circulation, oxygen and a constant supply of co2 since you're letting the water interface with the atmosphere better. 

You don't want to use an airstone if you're injecting co2 since the water's co2 will tend to equilibrate with the atmospheric co2, wasting your efforts.


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## cjyhc4 (Dec 18, 2006)

Jeffww said:


> Plants use oxygen just as much as they need CO2.....


If I remember correctly, O2 is required for the formation of CO2. 

Carbon from decaying plant matter, rotting food, waste, etc.
O2 from air or H2O


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## cjyhc4 (Dec 18, 2006)

Jeffww said:


> When plants photosynthesize they consume CO2 and produce O2 after stripping water of its hydrogens. However *they will still consume O2 and produce CO2* from cellular respiration *simultaneously.*
> 
> If you aren't adding CO2 to the tank through injection there is no risk to the plant's health, only benefits from increased circulation, oxygen and a constant supply of co2 since you're letting the water interface with the atmosphere better.
> 
> You don't want to use an airstone if you're injecting co2 since the water's co2 will tend to equilibrate with the atmospheric co2, wasting your efforts.


Yep, low tech, no added CO2, no ferts, etc


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## Jeffww (Aug 6, 2010)

They use O2 to live just like we need O2 and all othe aerobic life on earth. They have the added function of being able to incorporate CO2 into energy storing molecules. 


edit: Saw your post. What you're doing is just fine. I wouldn't worry about it.


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## BBradbury (Nov 8, 2010)

*Airstones*



cjyhc4 said:


> B,
> 
> Forgive me for not finding your reply particularly simple. Questions:
> 
> ...


Hello cj...

No problem. Hopefully, this explanation will clear things. Plants use the energy of sunlight to turn carbon dioxide and water into sugars and oxygen called "photosynthesis". This means that plants take in carbon dioxide (CO2) and give back oxygen (O2). O2 is the plant waste. Our fish do just the opposite. They take in the O2 and release CO2. 

So, it makes sense that you don't want too much O2 in the tank, if you want the plants to thrive. Just like you don't want too much CO2 in the water or it can become toxic to your fish.

Sorry for any confusion.

B


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## Darkblade48 (Jan 4, 2008)

BBradbury said:


> If you use several airstones in the tank, all the bubbles stir up the water surface and mix oxygen and water and release carbon dioxide. Oxygen is a plant waste product, so a high oxygen environment isn't ideal for good plant growth.


Not quite; the bubbles will stir up the water surface, and allow *gas diffusion* to occur faster. Oxygen is diffusing from a higher concentration location (the atmosphere) into a lower concentration area (water). The process is dependent on several factors, one of which is surface area. An airstone agitates the water surface, increasing surface area and hence increasing diffusion of oxygen (and other things, such as carbon dioxide).

Oxygen is not a plant waste product, per se, but is a byproduct of photosynthesis. Plants still require oxygen for aerobic respiration.

A high oxygen environment - unless you are actively injecting (pure) oxygen into the water, there is no harm to plants with normal atmospheric concentrations of oxygen.



cjyhc4 said:


> How does H2O + O2 yield CO2? Or are you saying that the movement of the bubbles forces the CO2 out of the water?


The first equation is incorrect, as mentioned above.

The bubbles increase surface area, causing the CO2 to diffuse from an area of higher concentration (the water) to an area of lower concentration (the atmosphere).



cjyhc4 said:


> Is this still a bad thing, if there is more CO2 produced than the plants can consume?


For example, if you are injecting CO2 at a rate that is higher than at which plants can consume it, the CO2 level will increase (assuming that it is not being off gassed due to agitation of the water surface). When it reaches a certain level, it becomes lethal to livestock.



cjyhc4 said:


> If I remember correctly, O2 is required for the formation of CO2.


This is a process known as aerobic respiration. CO2 is not formed, per se, but is produced as a waste byproduct during aerobic respiration.


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## mistahoo (Apr 25, 2012)

Don't plants take in oxygen at night or am I mistaken?


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## Jeffww (Aug 6, 2010)

They do it 24/7. Net o2 consumption at night.


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## AirstoND (Jun 17, 2011)

Air (oxygen specifically) is critical to redox stability of the tank ecosystem.

http://www.theaquariumwiki.com/Redox


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