# if no co2, air stone?



## pyrrolin (Jan 11, 2012)

If you don't run a co2 system would simply having an air stone benefit by providing some co2 from the air?

And the same thinking, would a tank with more surface agitation provide more co2 than a tank with low surface agitation?

my 90 gallon does not have co2 and has low surface agitation. Would my plants benefit from just simply adding an air stone? I know it wouldn't be a huge difference but would it be a noticeable difference?


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## charlie1 (Dec 1, 2011)

No scientific evidence for my train of thought, but I doubt it wold make a noticeable difference.
I`m thinking the co2 needs to de dissolved in the water, don`t see how it is going to happen , secondly the turbulence created may well void any co2 benefits if there is any.
Just a thought


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## pyrrolin (Jan 11, 2012)

anyone have some kind of device to measure co2 to test this theory?


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## Cichlidrookie (Apr 6, 2014)

Pyrrolin

Your idea seems viable but the is a small problem. Air is made up of so many gasses. Here are the percentages of those gasses. 78% nitrogen, 21% oxygen, 0.9% argon and then what u want 0.04% carbon dioxide. Not a lot of carbon dioxide in out air. So I don't think that will make any significance. Too bad we could not just use air stones. 

Hope this helps.


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## pyrrolin (Jan 11, 2012)

wow, I thought our air had more co2 than that. That small amount probably makes no difference and not worth the cost of running the air pump.


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## charlie1 (Dec 1, 2011)

pyrrolin said:


> wow, I thought our air had more co2 than that. That small amount probably makes no difference and not worth the cost of running the air pump.


Me too, the question is 0.04% of what volume?
I would think there is more than enough co2 in the atmosphere for the tree life to exist, just thinking off the top of my head, since this is not in my circle of friendly things to study


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## aniroc (Aug 23, 2012)

There is 100 times more CO2 in the air you exhale (4%); you are better off blowing air yourself


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## Cichlidrookie (Apr 6, 2014)

charlie1 said:


> Me too, the question is 0.04% of what volume?
> I would think there is more than enough co2 in the atmosphere for the tree life to exist, just thinking off the top of my head, since this is not in my circle of friendly things to study


Hey Charlie

With regards to your question about VOLUME? It does not matter because it is just going to be a percentage of that volume.

Example. For instance let's say you have 100 Cubic meters of air. That means only 4 cubic meters is CO2.

So volume does not really matter in this situation because it is still going to only be a PERCENTAGE of that volume.

Hope that clarifies your question.


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## fyns (Dec 22, 2011)

an alternate, and pretty cheap idea would be a manifold on your current co2 setup....

manifiold/NV/tubing/reactor/drop checker.


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## solarz (Aug 31, 2010)

Cichlidrookie said:


> Pyrrolin
> 
> Your idea seems viable but the is a small problem. Air is made up of so many gasses. Here are the percentages of those gasses. 78% nitrogen, 21% oxygen, 0.9% argon and then what u want 0.04% carbon dioxide. Not a lot of carbon dioxide in out air. So I don't think that will make any significance. Too bad we could not just use air stones.
> 
> Hope this helps.


Actually, 0.04% CO2 represents 400ppm, so yes, that is a lot of CO2.

Now, it doesn't mean you'll get 400ppm in water. It just means that by running an airstone, you will be continuously keeping your water CO2 at a constant level (atmospheric equilibrium).


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## pyrrolin (Jan 11, 2012)

so back to my question, would it benefit plants to run an air stone over just having nothing?

I am a long way from being able to get a good co2 system and wondering if it is worth it to put an air stone in my 90 gallon to get a little extra co2


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## aniroc (Aug 23, 2012)

My answer will be: no. In fact, I think its the opposite. By adding an airstone, you increase the contact surface between air (bubbles) and water. Its like saying that a 20G long has more CO2 than a 20G standard one because it has a larger contact surface with air.


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## solarz (Aug 31, 2010)

aniroc said:


> My answer will be: no. In fact, I think its the opposite. By adding an airstone, you increase the contact surface between air (bubbles) and water. Its like saying that a 20G long has more CO2 than a 20G standard one because it has a larger contact surface with air.


The idea about minimizing surface disturbance applies only when you are injecting CO2. In this case, you have a higher CO2 concentration than atmospheric equilibrium, so you want to prevent any additional surface gas exchange.

However, if you are not injecting CO2, you will have a lower CO2 concentration than atmospheric equilibrium, so any additional surface gas exchange will in fact be adding more CO2 to the water.

To answer the OP, I believe an air stone certainly would help. In fact, unless I'm injecting CO2, I always make sure I have plenty of surface agitation, to break up surface films if nothing else.


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## aniroc (Aug 23, 2012)

If you have any fish in the tank, chances are the equilibrium is already in your favor. Adding aeration, you'll drive more CO2 out than in.
The airstone inject air, same kind of air that the tank water has been already in contact at the surface, for which the equilibrium has been achieved. No extra CO2 will enter the water at the same temperature and pressure, unless there is more CO2 in the airstone's air.
Now, I need a pH meter to verify my point.


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## BillD (Jun 5, 2006)

The CO2 in the water will reach equilibrium with the air. As mentioned above, if a lot of CO2 is being used by plants, more will enter the agitated water than calm. So, while it may not be possible to exceed the concentration of CO2 in the air, maximizing the gas exchange will get it closer to that equilibrium.


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## aniroc (Aug 23, 2012)

Solarz: What makes you think that a nonCO2 injected tank has a lower CO2(aq) concentration than atmospheric equilibrium?


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## solarz (Aug 31, 2010)

aniroc said:


> Solarz: What makes you think that a nonCO2 injected tank has a lower CO2(aq) concentration than atmospheric equilibrium?


Because plants absorb CO2.


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## aniroc (Aug 23, 2012)

True. About 20% of which is released back at night.
How about fish or bacteria?


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## solarz (Aug 31, 2010)

aniroc said:


> True. About 20% of which is released back at night.
> How about fish or bacteria?


CO2 being released at night does not help with photosynthesis. The purpose of an air stone is to provide a stable level of CO2 throughout the day.

As for fish or bacteria, keep in mind that bacteria population depends on the bioload, so it's really about the fish load of the tank.

Fishes produce both nitrates and CO2. Plant growth can be limited by either. If there are excess nitrates in water, and injecting CO2 improves plant growth, then that means plants are being limited by CO2 and not by nitrates. If the reverse was true, then we would be seeing 0 nitrates, and plant growth would not improve if we only injected CO2 but didn't add more nitrates.

Therefore, fish produce more nitrates than CO2, relative to plant consumption. Assuming light isn't a limiting factor, then when we see excess nitrates in the water, that would logically mean CO2 levels are limiting. If CO2 levels are limiting, then it's not a wild leap to guess that the CO2 levels are lower than atmospheric equilibrium.


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## DWD (Dec 29, 2013)

Interesting topic. I had the same thought and tested it in my tank. 

About one month ago, I put some Red Fire shrimps and horn snails in my grass tank for some reasons. After one week, one snail was dead and the shrimps were not activating. I put an air stone in the tank and stopped CO2. I thought the air stone might be able to support both plants and livestock.

I kept testing the water quality daily. After one week, pH raised from 6.5 to 7.5 (expected), and NO3 dropped from 20 to 0 (no idea why), other data, GH (150), KH(80) and NO2(0), almost kept same.

The livestock is happen and move around. However, I found the new grown part of grass (dwarf hair grass and dwarf HC) was not as same green as before, they were a little white-green. And some grass became a little yellow. I am not sure that it was because of lacking CO2 or the plants didn't get used to the environment change.

Anyway, now I think the CO2 cannot be replaced by air stone in a plant tank if you want the plants to be beautiful and grow fast.

Hope this is helpful.


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## pyrrolin (Jan 11, 2012)

DWD, those plants do best with some co2 and I recommend a co2 system with them.

I am not asking about replacing a co2 system with an air stone. I know that an air stone won't even compare to a co2 system.

This discussion is on if a tank with no co2 system would benefit from an airstone


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## solarz (Aug 31, 2010)

pyrrolin said:


> DWD, those plants do best with some co2 and I recommend a co2 system with them.
> 
> I am not asking about replacing a co2 system with an air stone. I know that an air stone won't even compare to a co2 system.
> 
> This discussion is on if a tank with no co2 system would benefit from an airstone


My belief is that while it will benefit, you can achieve roughly the same effect with good surface agitation (i.e. HOB filter). Since the only goal is achieving atmospheric equilibrium, surface agitation is usually enough.


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## aniroc (Aug 23, 2012)

I have a different vision but I totally enjoy the debate.
I believe the purpose of an airstone is to provide oxygen, not CO2. It is mostly accepted in a CO2 injected tank, during the night when plants also need oxygen. The loss of CO2 in this case is not a concern since more will be injected in the morning.
I also believe that as long as there is life in your tank, there is more CO2 produced by fish, snails but mainly bacteria braking down organics than diffused from air, thus, you'll have more, not less than atmospheric equilibrium according to Henry's Law.
I wish it was that simple....
The are natural water environments with toxic levels of CO2 (bogs come to mind). However, those waters are acidic and high in carbonates. Because CO2 (unlike O2 or N2) doesn't just dissolve in water but it reacts with it forming "carbonate hardness". The CO2 in the water is now at yet another equilibrium with carbonic acid, bicarbonate and carbonate.
This is why, while you cannot add more CO2 with aeration, you can deplete the little you have, along with carbonate/bicarbonate.
Note: Do not mistake me for someone that understands it all


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## pyrrolin (Jan 11, 2012)

I wish someone had some kind of meter to fully test this accurately. Both sides have valid points but we need some hard evidence.


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## hendy8888 (Sep 10, 2010)

I don't think there would be any noticeable difference in the plants between an air stone or not for co2 in a low tech tank. Surface movement is always good to have though so if you like bubbles put the air stone in, if you don't then aim the filter output at the surface a bit. 

Sent from my Nexus 7 using Tapatalk


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## KeyLime (May 4, 2014)

OK, gotta necro this thread!

Was thinking about how much CO2 the fish make, and then how much is in shiipping bags, and then...

Kordon:


> Carbon dioxide exits the bags at 4 times the rate oxygen enters the bags, thereby constantly purging the water of toxic carbon dioxide, and allowing oxygen to replace it in the water.


So what happens if you use an air pump to Kordon Breathing bags in the tank ?
Is the air concentration of CO2 just too low to make a difference? I guess if the bag could dump it's supply of air every so often it might work a bit.

I just want free CO2 
Maybe in the future we'll have R/O-like CO2 filters.

http://pubs.rsc.org/en/Content/ArticleLanding/2013/TA/c3ta13066e#!divAbstract



> In contrast to the performance of conventional materials, the selective layer of TFC membranes shows super-permeable characteristics and outstanding CO2 separation performance.


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## pyrrolin (Jan 11, 2012)

I have my regulator and stuff now I just have to confirm the connection size for a co2 tank and come up with the $100 or so for a 10 lb tank.

With luck I can cheaply split up the output to do a couple extra tanks with the same rig.

I am moving so I had the co2 system delivered to my parents place in case it took too long to ship so I haven't even seen it yet and even when I do see it, I have no clue. I'll be posting for advice in a week or so once I have it in hand.


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## Lee_D (Jun 11, 2010)

I would have thought the more pertinent question would have been is the tank covered or not covered?

If it is covered, the surface circulation has little effect because the air above the tank does not change significantly. An Airstone would be helpfull.

If it is uncovered, the tank equilibrates with the outside air, and the airstone is thus not necessary.

The CO2 is consumed during the day, and produced at night. You want to add it during the day, and add O2 at night. Airstones / uncovered tanks will stabilize the concentrations of these gases as they are required.

Lee D


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## aniroc (Aug 23, 2012)

I see this thread is active again and meanwhile I found a reference to share:

"Many aquatic plants could not survive in nature without the CO2 provided by decomposition. Water in equilibrium with air contains only about 0.5 mg/l (ppm) CO2." Diana Walstad: "Ecology of the Planted Aquarium" page 100


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## KeyLime (May 4, 2014)

aniroc said:


> I see this thread is active again and meanwhile I found a reference to share:
> 
> "Many aquatic plants could not survive in nature without the CO2 provided by decomposition. Water in equilibrium with air contains only about 0.5 mg/l (ppm) CO2." Diana Walstad: "Ecology of the Planted Aquarium" page 100


While it's true that the atmosphere is currently CO2-poor for plants, terrestrial plants seem to do OK without supplementation at even 350 ppm, now roughly 400 ppm. They say below 200 ppm or so means disaster.
I think in water it's got to do with "equilibrium" vs. the pressure and so on. The temperature and depth of the water plays a role I guess. "Equilibrium" here might not mean "equal".


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