# Why is CO2 misting so effective?



## John N. (Dec 11, 2005)

Over the past year, CO2 injection through glass diffusers, limewood and airstones have revolutionized the way we think about CO2 injection. The goal of C02 misting is to have tiny C02 filled bubbles blown around so that they can 1) dissolve quickly and 2) stick to plant structures as it is believed that the direct contact makes it easily absorbed by plants. New glass diffusers of all shapes and sizes are storming the market and are frequently recommended to new hobbyists. There is also a growing trend away from internal reactors and inline reactors because of this injection method. Why is C02 misting so much more effective than our previously favored turbulence driven, complete CO2 dissolution reactors? Are glass diffusers and C02 misting more effective, and should we be recommending them over reactors? 

This brings up another related thought. The continual duelist perspective C02 mist verses Reactors dominates the planted aquaria scene and have forced the hobby to become neglectful of innovation. What other methods/ideas have yet to be explored and haven't due to our thinking complacency? 

-John N.


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## hoppycalif (Apr 7, 2005)

If you are interested in driving the plants to grow as fast as they can, then I think CO2 mist is the way to go. Each bubble of CO2 carries with it extra enriched dissolved CO2 right around the bubble, so even if the gas doesn't feed the plant directly, the locally high concentration of CO2 in the water around the bubble does. When I used it I had my maximum plant growth rate. But, with that comes less clear water, both due to the CO2 bubbles and due to the greater pearling which contributes more bubbles to the water. 

The rapid growth of the plants makes pruning even more critical as the added plant mass soon disrupts the water and CO2 bubble circulation in the tank. And, if you are looking for maximum growth rate you are using high light intensity too, which makes all of the tank maintenance more trying if you want to avoid algae.

So, I enjoyed the mist experience, just as I used to enjoy driving a Porsche rapidly on winding country roads. But, it soon becomes more of a problem than a benefit.

I now use an external reactor, much lower light intensity, and I get more enjoyment from the hobby. I'm sure there are many who would have a different opinion about driving a Porsche on winding country roads - or CO2 misting.

My opinion only is that the next "innovation" in CO2 use will be cutting back to some lower "ideal" concentration, such as 20 ppm, but running it 24/7.


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## Freemann (Mar 19, 2004)

Well let me trace back misting, Amano did it first but he used it in combination with rich substrate,plus basically K, TE, Fe fertilizing regime he used this regime with reactor diffusion with similar results I think. Then came Barr and he suggested it as a measure to increase health and growth of plants I personnaly think both ways work as long as the ferts are in balance, reactors are surely more economic CO2 wise, and diffusers turn the tank to Champagne, all I know is that if some fert is in imbalance a ton of CO2 won't remedy the problem this way or the other it will probably worsen it by accelarating one growth factor.


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## mikenas102 (Feb 8, 2006)

While misting is not as efficient as a reactor, it certainly is more user friendly. A well built reactor can be 100% efficient with the CO2 injected. Even the best diffusors will still have bubbles that reach the waters surface and therefore wasted. If you accept the fact that you'll use a little more CO2 to reach your target level, a diffusor is much easier to use. It requires no inline plumbing modifications or extra powerheads and does not inhibit the flow from your filter since it completely independent of it. Cleaning a clogged diffusor is much easier than if you ever had to clean out a clogged reactor. The other drawback of misting is of course the aesthetics. Some people like the way it looks, others don't. That aspect is a matter of personal opinion.


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## BryceM (Nov 6, 2005)

Are we all agreed that misting is better than dissolution in a reactor? I'm not convinced.


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## Freemann (Mar 19, 2004)

I'm not convinced as well.


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## hoppycalif (Apr 7, 2005)

guaiac_boy said:


> Are we all agreed that misting is better than dissolution in a reactor? I'm not convinced.


"Better" is a subjective way to describe it. I believe you get the maximum growth with high light and CO2 misting. I don't consider that to be "better" from my point of view.


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## houseofcards (Feb 16, 2005)

I would agree that better is subjective. I mean in certain situations one might be better off with Excel than both misting and complete dissolution. For example I have a 5g nano with a riccia foreground. With Excel it grows at a slow rate and I don't have to worry about it for about 3 months. If I used misting on this particular tank the riccia would grow faster of course, but also gain buoyancy by all the pearling and it would detach much quicker. Just one example, but I'm sure there are many others. 

From an aesthetic point of view, on my other tanks I like the little bubbles. For me it makes the tank seem more alive, more dynamic. I think people are also attracted to the simplicity of a diffusor as opposed to a powered or inline reactor.


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## Zapins (Jul 28, 2004)

I'm also not convinced that misting is more effective.

Inline reactors reduce bubble size to microscopic levels, the surface area of those "bubbles" is nearly infinitely larger than mist bubbles - which means more surface area that the CO2 gas can dissolve into the water (and surround plant tissue). 

Seeing larger mist bubbles sticking to the plants may make it seem like the misting method is better but if you could see each microscopic bubble of reactor CO2 I would warrant a guess that there would be hundreds more reactor bubbles on the plant.

Anyways, I suppose there is no real empirical test that would satisfy our questions, but inline reactors definitely need less cleaning/maintenance than those glass diffusers. Not to mention the best part - its out of sight!!!!


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## ponyrandy (Jan 13, 2007)

I always thought that the goal was to get the co2 dissolved into the water column as much as possible. I think that the glass diffusers are more popular for two reasons: (a). they are cheaper than a reactor, and (b). they are very simple to use, just hook up the co2 hose and stick it in the tank.
Brian


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## hoppycalif (Apr 7, 2005)

Let's be honest - one reason for the popularity of glass diffusers is the ADA versions, which are elegant looking and have the cachet of being marked as ADA products. Psychology is always part of what makes something popular. (Or, by definition, maybe it is everything.)


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## Zapins (Jul 28, 2004)

Yea marketing psychology definitely plays a huge role. 

Also I'm not sure if the glass ones are actually used more than inline reactors, might be an interesting poll?


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## Muirner (Jan 9, 2007)

guaiac_boy said:


> Are we all agreed that misting is better than dissolution in a reactor? I'm not convinced.


I'm agreeing here, i dont believe that misting is better then a reactor. Why do i say this? Because most people using a misting device (limewood, air stone, even a diffuser) use about 3+bps to achieve 30ppm of CO2 in a 55gallon tank (at least that's what ive found around forums). With my inline reactor, i can run it at 1 to 1.5bps and acchieve 30ppm. This allows the co2 to disolve 100%... Just my experience.


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## houseofcards (Feb 16, 2005)

Muirner said:


> I'm agreeing here, i dont believe that misting is better then a reactor. Why do i say this? Because most people using a misting device (limewood, air stone, even a diffuser) use about 3+bps to achieve 30ppm of CO2 in a 55gallon tank (at least that's what ive found around forums). With my inline reactor, i can run it at 1 to 1.5bps and acchieve 30ppm. This allows the co2 to disolve 100%... Just my experience.


O.K. there's two different thoughts going on here. One is efficiency and the other is performance. 
Co2 misting might not be as efficient, but do the plants look and grow better compared to an inline reactor.


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## Muirner (Jan 9, 2007)

I wish i could say, but honestly i dont have the experience, and my school dosent allow fish tanks so i wont be able to experiment.


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## Roy Deki (Apr 7, 2004)

I myself started with a Plant Guild Power reactor and I will say from my observation that this is a much more efficient method of co2 diffusion. Mush easier to kill live stock with this method. I now use only the glass ceramic diffusers because the plants seem to grow better and faster. The reason I believe this is true is because of the direct contact of the bubbles on the plant leaves. This is just an observation of my own experience and I have no scientific data to back this up. "If it isn't broke don't fix it." LOL


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## mrkookm (Oct 25, 2006)

Since I began misting via R5k I too have seen the better growth from my plants and more importantly I'm finally able to maintain stable Co2 ppm in my *sump setup* with realistic _*bps*_.


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## Bert H (Mar 2, 2004)

Chiming in a little late on this one, but I am another one who has not had the experience that misting is better than a reactor. I tried a diffuser on my 10 which had previously had the CO2 injected into the intake of my AC HOB. I saw no difference in any measurable (by my eyes) factor. No better or faster growth, no less useage of CO2, no less gda to wipe off the glass. All I had after a month was a diffuser which was getting green and another gadget in the tank I didn't want to look at. My 2 cents.


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## houseofcards (Feb 16, 2005)

And of course, to make things more interesting we have a "blending" of the two. The in-line diffusor:










Anyone use one yet?


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## John N. (Dec 11, 2005)

Very interesting discussion we have here. I agree, 100% dissolution cannot be reached with CO2 mist, and so therefore reactors offer a more efficient use of CO2. However, performance wise like Roy and Mrkoon, observationally, I've seen what appears to be healthier and more robust plant growth with CO2 mist as oppose to the Plant Guild Power Vortex Reactors. Yet, Bert and some others mentioned that they didn't see this effect.



hoppycalif said:


> Each bubble of CO2 carries with it extra enriched dissolved CO2 right around the bubble, so even if the gas doesn't feed the plant directly, the locally high concentration of CO2 in the water around the bubble does. When I used it I had my maximum plant growth rate. But, with that comes less clear water, both due to the CO2 bubbles and due to the greater pearling which contributes more bubbles to the water.





Zapins said:


> Inline reactors reduce bubble size to microscopic levels, the surface area of those "bubbles" is nearly infinitely larger than mist bubbles - which means more surface area that the CO2 gas can dissolve into the water (and surround plant tissue). Seeing larger mist bubbles sticking to the plants may make it seem like the misting method is better but if you could see each microscopic bubble of reactor CO2 I would warrant a guess that there would be hundreds more reactor bubbles on the plant.


Aesthetics and ADA marketing aside which I believe also is a major contributor to the popularity of misting type diffusers, is the interaction that Hoppy described the reason for this increased performance in our tanks and so many other cases? I believe Zapins makes a great point that we should also consider about reactors having the same, if not more beneficial interaction between plant absorption and C02 bubble contact. If this is true, why don't we see a "champagne" effect with reactors?

And then House also brings up the Cal Aqualabs innovative inline diffuser product that blends the two methods. I'm curious to see how that is performing since surely it dissolves a large amount of CO2 and disperses the remain as CO2 mist. Maybe that's the thinking we should be further exploring?

-John N.


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## hoppycalif (Apr 7, 2005)

Don't we first have to more carefully define our goals? Efficiency, meaning the use of the lowest bubble rate to get to the concentration of CO2 in the water that we want, is one goal, but not one that interests me. Obtaining the most rapid growth of the plants is another goal. Achieving as much pearling, as quickly as possible is still another goal (probably the same as the rapid growth goal). Minimum maintenance of the CO2 system is another goal. And, esthetics is still another goal. My goal has evolved to minimum maintenance and ease of maintaining stable CO2 concentration in the water. I think the external reactor meets that goal.


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## mrkookm (Oct 25, 2006)

> Don't we first have to more carefully define our goals?


Yes I agree totally...mine was efficiency. My goal was to be able to maintain stable Co2 ppm in a non-friendly Co2 sump setup which I must say is more difficult a task than trying to do the same with a canister filtration setup. IME direct misting got me there more efficiently 'less _bps_ required' and my plants responded very well. Is it because misting is better? I don't know and maybe not  Was it because I finally got Co2 where it needed to be? That i'm pretty sure it made all the difference.

My main goal was to stop making trips for refills every 3weeks I was happy that I finally was able to do so. Esthetics though a factor is not a major one for me & maintainance...well I've gotten used to it. My plants looking happy is as major as it get for me and mine are now after misting...if my plants are happy I'm happy 

Wouldn't it be better to say?

*Reactors best used with* = Canister or any other type of closed loop filtration
*Misting via Venturi, Glass Diffusers, Limewood, vortex, etc* = any type of sump, high flow or non-friendly big tank setups


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## ponyrandy (Jan 13, 2007)

Isn't co2 in real life dissolved in the water column and not misted in bubble form?
Brian


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## hoppycalif (Apr 7, 2005)

ponyrandy said:


> Isn't co2 in real life dissolved in the water column and not misted in bubble form?
> Brian


CO2 will certainly dissolve into the water, no matter how you deliver it to the tank. But, CO2 mist is tiny CO2 bubbles, being blown around the tank into the plants. It is reality too. Much of the CO2 mist ends up floating to the surface to be wasted, so it necessarily uses more CO2 per ppm dissolved in the water than reactor usage does.


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## Supercoley1 (May 28, 2007)

I use CO2 mist from a Rhinox diffusor.

This was from reading several views on them and long before I discovered the barrreport.

I initially used it with 3 DIY yeast kits under 2.5WPG. I then used it with pressurised under 2.2WPG and I currently use it with pressurised under 1.8WPG.

I think the statement about bps earlier can be a little misleading. I don't think that anyone can dispute the fact that a reactor is more efficient. What can be disputed is how in nature the CO2 is transported. I would suggest as the CO2 is taken from the air and carried through the water that it is probably morelikely to be in bubbles as it will be drawn into currents etc. I am no scientist and this is purely speculation.

With the yeast I got 30ppm from 3bps, under 2.5WPG the pressurised was set to 4bps to give 30ppm (with fast growing plants in the tank) I currently run it at 1bps for 24 hours with slow growers under 1.8WPG to achieve 30ppm.

The bps is in effect proportionate to usage which is of course driven by light, ferts andthe type of plants you are using.

I have always had good growth in all 3 setups but have never tried a reactor so I have nothing to compare with. I just feel this works for me so why change.

I use Glass Lily pipes and the lily's voretex pulls the surface water (where the bubbles that reachthe surface are) into it and blasts them around the tank at microscopic levels.

The 2.5WPG tank was like champagne from pearling and CO2 in the tank whereas the current setup has no champagne appearance at all. Same diffusor, same CO2 setup only 0.7WPG less but different plants and much lower bubble rate plus run for24 hours and not on solenoid. What conclusions can I draw from this? I don't know but its working so I don't worry.

(And they look damn good)

Andy


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## mrkookm (Oct 25, 2006)

> I think the statement about bps earlier can be a little misleading.
> 
> The bps is in effect proportionate to usage which is of course driven by light, ferts andthe type of plants you are using.


I agree supercoley1 but remember I not comparing different tanks nor did any of the above change except the method of diffusion. The same _bps_ that was pumped into my reactors was used initially in my glass diffuser. During the first 2 days of tryout my DC went yellow multiple times (something that never happened when using any of my reactors) as I was 'finding my new lower bps rate. BTW I had and still do have my DC mounted 5" from the substrate and I use a commercial prep'd solution.


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## Supercoley1 (May 28, 2007)

my drop checker is situated in the front right of the tank with the entry hole about 5 inches from the surface and 10 inches from the substrate.

My diffusor is situated in the back right corner with the Lily in and outflow in the same corner.

I use a homemade 4dKH solution which is blue when first mixed and is green in my tank (and went bright urine yellow the day CO2 killed al the livestock in my tank whilst at work when for some reason a dodgy needle valve alowed the whole cylinder (2 days old) to discharge.

Therefore I think I can assume that the solution is OK.

I keep it at a limeade colour all the time and change the solution every 3 weeks.

Andy


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## Bill Weber (Jul 17, 2005)

Zowee what a great discussion.

I have tried several methods of distrubuting co2 into my 70g.

1. Membrane - With this device I saw very little increase in plant growth. No pearling at all.
2. Aqua-Medic Reactor - Better plant growth. No pearling. Had trouble keeping the bubbles riding the rollercoaster.
3. Inline atomizer - Plant growth was OK. little pearling. Eventully, plant growth slowed and pearling disapeared.
4. Glass Defusser - Nice to look at but not much better than the atomizer.
5. DIY Misting - I inserted the co2 into the intake of a Rio 10 to blow co2 through the 4' tank. I reduced the bps to 2. co2 checker is green. Plants show much better growth. Pearling is better but not like some tanks I have seen. I do not much care about the ph in my tank but it is now running at 8.8ph instead of 9.1. I thought the ph would reduce more that it has.

Summary - Misting is working for me better that any other method I have tried.


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## Muirner (Jan 9, 2007)

My question becomes now. How come misting is "so effective" If both enable the plants access to 30ppm of CO2 in the water collum, what would cause the misting to be "more effective" then using a reactor? 

In nature, if we observe, no co2 is misted into the environment, it's there. Surrounding the plants. It is available to them and they can use it how ever they deam necessary. And with the water having a set ppm of CO2, why would growth rates differ?


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## Steven_Chong (Mar 17, 2005)

The point is that they both work, right? As long as the plants are growing gangbuster and healthy, I'm happy . . . 

My goal is to take a 3 month school semester, and use it to make a fully developed scape capable of ranking in the tops of any aquascaping contest, and also satisfying my creative passions/outlets.

In which case optimal growth rate is best-- I got the passion and obsession to fuel any need for maintenance; which includes the half-mile uphill walk to the library where my tank is housed. Well, others probably have different desires for the hobby than me . . . Hoppy isn't a 21 year old college brat anymore. lol I got to salute the dedication and wisdom a guy his age is still putting into the hobby and giving back to everyone else.


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## BryceM (Nov 6, 2005)

Is anyone aware of any actual experimentation on this to see if it makes a real difference when other factors are carefully controlled? Anecdotal evidence is no evidence at all. ADA and certain other people certainly have a reason for you to think that it makes a difference. I'd really like to know if it does, but even more I'd like to know through what mechanism such improvement might be acting. To my scientific mind nothing that I've heard yet seems plausible.

Keeping an open mind...... but I'd like to see some actual data.


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## nanobettaman (Sep 6, 2007)

Muirner said:


> My question becomes now. How come misting is "so effective" If both enable the plants access to 30ppm of CO2 in the water collum, what would cause the misting to be "more effective" then using a reactor?
> 
> In nature, if we observe, no co2 is misted into the environment, it's there. Surrounding the plants. It is available to them and they can use it how ever they deam necessary. And with the water having a set ppm of CO2, why would growth rates differ?


I'd wager that the misting, while showing a 30ppm level in the drop checker, actually gives the plant much more co2 because the bubbles are pure co2. Any bubbles in contact with the plant are providing a direct shot.

I'm using a hagen elite mini filter to blast bubbles around the tank (running just under 1bps in a 15g) some bubbles are making it to the surface eventually, but many others are sticking to the plant and/or getting stuck in the undersides of leaves. This would be giving the plant much more co2 than whatever manages to get dissolved into the water column


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## Supercoley1 (May 28, 2007)

to plageurise (maybe a spelling mistake) from a thread on another forum that I shall not name. lol

It was suggested that it is something to do with gases travelling faster than water and also something about the gas bubble being able to break through a boundary layer around a leaf easier than the water dissolved CO2.

Most threads on 'said' site suggest that it is not really known which way is better just that they are 2 choices and it seems the general consensus seems to be if you don't want to see little bubbles then use a reactor, if you want to see bubbles then use a diffusor, if youre not fussed use either.

I guess similar to if you don't want pearling then use lower lights.

I guess you can get some idea of what happens just from seeing the amount of bubbles I get in my tank just by raising the Lily pipe to break the surface up a little. I get probably 100 x the amount of bubbles that come from my diffusor buzzing all around the tank and you can see how they stick to plants and to hardscape and indeed to anything that is solid.

Maybe what is needed is someone to plant 2 identical tanks with the same fert regime, same filter and currents, same temperature, same lights andto plant plants from the same batch in exactly the same positions in each tank.

Then maybe someone can tell a diffeence wether it be healthier growth, faster growth, better colours or whatever.

Maybe a project for someone who has the time and tank and equipment. lol

Andy


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## hoppycalif (Apr 7, 2005)

It is extremely hard to set up two identical tanks, because there are so many things that can affect how well plants grow in a tank, and how much algae you get. I wouldn't even think of trying to check a single variable that way unless I first proved to myself that I could set up two identical tanks and get identical results in them, and I know I can't do that now.

One thing we should be trying to do, I think, is establish a variety of "good" things that can be done, from fertillizing to CO2 injection, to substrates, to lighting, etc. Then each of us just has to try things to find what works best for each of us. And, as we have said, the definition of "best" is a personal one.

From what I have read, a lot of people have tried CO2 mist and been pleased with the plant growth that follows. So, there does have to be some benefit to using it. The benefit comes with "baggage" though, such as having a tank always filled with bubbles. So, you should consider the trade-offs, try it if you think the trade-offs are largely positive, and if you don't like the result, try something else. This isn't a "one size fits all" hobby.


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