Moving Beyond CO2 Injection? - The Planted Tank Forum
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post #1 of 20 (permalink) Old 05-16-2019, 07:36 PM Thread Starter
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Lightbulb Moving Beyond CO2 Injection?

Hello,

So full disclosure, I have never run a high tech tank, though I am in the planning stages of my first. I was/am planning to run injected CO2 from a 10 lb tank via a DIY reactor.

While I was thinking about this I began to wonder if "Injected" CO2 is necessary for any plant we might want to grow. In nature there is no injected CO2. Instead you just have really large bodies of water possibly with enough flow that what CO2 is naturally in the water from surface contact is enough to keep plants alive. Or at least that is my theory. I actually have no idea for certain where CO2 comes from in natural water. Maybe its all from dissolved rocks? Who knows. Anyway if it comes from the air then I wonder if we could replicate the process in our tanks by running an airline into a big reactor.

If we can dissolve enough air in a reactor into our water then could we replicate the natural CO2 environment that all of our plants originated in?

If this would work then the benefits would be substantial. 1) We would not need to have pressurized gas in our houses, 2) We would not need to buy CO2 anymore, 3) It would be impossible to gas our fish since we would actually be oxygenating the water at the same time, 4) You wouldn't need a solenoid anymore because it wouldn't matter if it ran all the time.

There are some downsides. 1) You would need some kind of air pump which would make noise, 2) while plants may live fine you likely could not get the concentrations of CO2 in the water with dissolved air as you would with CO2, 3) You need a BIG reactor since apparently air does not dissolve in water as easily as CO2.

This is not completely off the wall on my part. I was watching videos on venturis and I kept running into people in hydroponics making use of them to aerate their water. Apparently its super important for them to get good growth. I also saw a video from Aquarium CO-OP where Cory was speculating that sponge filters are good for plant growth because they are constantly bringing in air which has CO2 in it. And finally I saw a video about a gas "contactor" cone which was being used with room air to oxygenate water for waste management. The air was being completely dissolved into what we would call a reactor. This idea spawned from all those.

Has anyone ever tried this?
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post #2 of 20 (permalink) Old 05-16-2019, 09:15 PM
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Hi @minorhero,

No injected CO2? Sacrilege! Blasphemy! Perish the thought! Don't you dare take away my bottle! J/K.
What I feel about this is similar to what I wrote about in another thread: https://www.plantedtank.net/forums/2...l#post11205137

The gist of it is... our tanks, ironically, are not natural. Especially the really nicely scaped ones with odd plants. A lot of our plants would rather grow out of water, but we admire their in-water form instead, so we force them to stay underwater. Then, some of our plants have been gathered from far corners of the world where co2 concentration is markedly higher than equilibrium. So, for a lot of us, we have created this artificial need for serious co2 injection due to our own collectoritis and the way we want to present said collected items.

Or perhaps, see this site with a more in depth explanation. https://www.advancedplantedtank.com/...g-co2-why.html

If you run a low tech tank with simple plants, I have no doubt that you can do quite well with equilibrium amounts of CO2.
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post #3 of 20 (permalink) Old 05-16-2019, 10:11 PM
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In hydroponics it is very important to keep O2 levels up.. Plants really don't drowned but the water replaces air (O2) spaces..

You need to remember that CO2 is just like fertilizers..and is as necessary or not as that is.

We like to control things and injection has more control than hoping our gas exchange due to turbulence is adequate..

Use or not depends on ones goals..

Injection isn't to get it always to air equilibrium which seems what you could do best, at best, but increase above equilibrium.. anyways it's complicated.. like this:
pH of Water with dissolved Carbon Dioxide and Calcium
https://eos.org/research-spotlights/...xide-in-rivers

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Last edited by jeffkrol; 05-16-2019 at 10:34 PM. Reason: edit
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post #4 of 20 (permalink) Old 05-16-2019, 11:26 PM
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Decomposition of organic carbons in deep lake or ocean beds where water is colder and also under very high pressure is also a major pathway for CO2 in nature. Every shoreline and pond bottom also breaks down carbon sources and releases CO2 back into the water as well.

Many pathways in nature for adding CO2 including weathering of carbonate bearing stone etc.

All part of carbon cycle.
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post #5 of 20 (permalink) Old 05-17-2019, 12:37 AM
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Quote:
Originally Posted by minorhero View Post
Has anyone ever tried this?
Maybe.

But if it actually worked, I am sure you would see loads of beautiful healthy tanks using it.

For someone starting out, best advice is to find tanks of similar size and goals to your own. Study their methods, and it will give you a head start.

I am pretty certain you will not find a single one doing what you described above.


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post #6 of 20 (permalink) Old 05-17-2019, 12:55 AM Thread Starter
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Thank you Jeff for the link! and thank you Dave for the shortcut. The data Jeff provided essentially say the same thing. Studies of streams showed that water coming from underground was high in CO2 and once it reached the surface it began to dissipate. The study was mostly about buffering but it made clear that CO2 was from the breakdown of organics after the water as at the surface. Downstream had lower levels of CO2 then upstream which would not have been the case if CO2 was primarily coming from surface exchange with the air.

Soooo, not what I was thinking.

Back to just using pressurized CO2. Thank you folks for the feedback and info.
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post #7 of 20 (permalink) Old 05-17-2019, 03:59 AM
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I heard Cory mention this and itís pretty straight forward to test; run a tank with out air and then add air and see if the ph drops in any noticeable way over a short time period (couple of hours) so as not to confuse a lowering ph with nitrate build up. In theory yes of course co2 is being added when pumping in air from our environments but not to the levels that the above people mentioned we need for what we typically strive for in a Planted tank. Check out the walstad method as well as it is another way to make carbon available to plants by breaking down the soil over time with bacteria instead of using remineralized top soil which speeds up that process to avoid algae issues as well as make the nutrients in soil more available quicker.


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post #8 of 20 (permalink) Old 05-17-2019, 03:21 PM Thread Starter
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Quote:
Originally Posted by Willcooper View Post
I heard Cory mention this and itís pretty straight forward to test; run a tank with out air and then add air and see if the ph drops in any noticeable way over a short time period (couple of hours) so as not to confuse a lowering ph with nitrate build up. In theory yes of course co2 is being added when pumping in air from our environments but not to the levels that the above people mentioned we need for what we typically strive for in a Planted tank. Check out the walstad method as well as it is another way to make carbon available to plants by breaking down the soil over time with bacteria instead of using remineralized top soil which speeds up that process to avoid algae issues as well as make the nutrients in soil more available quicker.


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I probably will run an experiment when I setup my new tank since its so easy to do. I will just test water out of the tap, test it after it out gasses, then run my reactor with an air pump instead of co2 and test water again. If there is a significant increase in co2 then it could become a cheap way to get healthier plants without needing co2 even if co2 reins supreme.

I would normally love to do a dirted tank but my next tank will have a crayfish in it which means I really need a homogeneous substrate. I have no desire to do a low tech tank at this point, I just enjoy the DIY aspects of the hobby plus trying out new ideas.
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post #9 of 20 (permalink) Old 05-17-2019, 03:38 PM
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A small point to keep in mind is that greenhouses and weed growers who want increased growth also add increased CO2 to higher than free air levels. So when we want more growth than the low tech tank, we do often need more CO2 than we can get from the air.
And, yes, it is certain that lots of folks have tried it as there are so many who would rather not have the trouble and expense of adding CO2. Kind of like inventing the wheel and then somebody comes along to ask if it's really needed? If it was not needed/useful, most would not be doing it!
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post #10 of 20 (permalink) Old 05-17-2019, 03:59 PM Thread Starter
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/shrug I can't help but suspect that most inventions look obvious in hindsight to those familiar with the technology. Someone built the first DIY CO2 reactor and then shared it. Pretty soon everyone was building them. The price of entry into this experiment will be an air pump and a few days. All other parts I will be assembling for my DIY CO2 reactor anyway. I am already planning to build a large reactor.

Certainly everyone with an air stone is doing this experiment already but only to a very limited extent. In order to make this work you need to dissolve a lot of air which means a reactor. If this works then that would be the reason why folks haven't figured it out before. I mean, how long have we been building large CO2 reactors to keep plants? 20 years? Less? Certainly the internet has not been disseminating this information widely much longer then that.

Anyway it sounds like fun! So why not?
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post #11 of 20 (permalink) Old 05-27-2019, 01:39 PM Thread Starter
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UPDATE

I thought about this a lot and decided that the only piece of equipment I would need to make it work that would not be reusable on a new tank I am planning is the air pump. Everything else is needed to run co2 so why not give it a go?



There is my reactor. Using a 5 gallon bucket as a "tank". Obviously nothing in it but a pump. I purchased the lamotte co2 test kit to determine co2 levels. There are few options for determining co2 levels precisely I was surprised to find. Drop checkers being too general.

RESULTS

My tap water had about 2ppm co2 out of the tap. This never went away even when allowed to sit in the bucket for more than 24 hours. My guess is that this is essentially surface exchange levels of co2.

After hooking up the reactor with a whisper 40 air pump and letting it run for 4 hours I found the levels of co2 to be 3-4 ppm. Soooooo yeah it worked, just not well enough to be of any use to us. It is possible that the itty bitty air pump I used simply was not strong enough to provide enough air to make a difference. I admit to being very underwhelmed with it's performance. But I am not sure if I will buy a larger one. The air pump only cost 10$ so not out a lot of money so far. I did put a bid in on a regulator on eBay right after getting these results. I think that tells you how confident I am in getting better results. 😉
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post #12 of 20 (permalink) Old 05-28-2019, 03:35 PM
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I almost always run an airstone in my low tech setups, some time in the sumps. My thought is that while CO2 concentrations are relatively low in water relative to air, plants taking up the CO2 that is there will deplete them, and perhaps this will at least keep levels at a constant. I thought about using a reactor as well, but was hesitant since I have read about negative effects on fish when gases become supersaturated.

ďScience, my lad, is made up of mistakes, but they are mistakes which it is useful to make, because they lead little by little to the truth.Ē -Jules Verne
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post #13 of 20 (permalink) Old 05-28-2019, 04:15 PM
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Quote:
Originally Posted by minorhero View Post

My tap water had about 2ppm co2 out of the tap.

1) What is the pH of your tap water?
2) What is the pH of your 'bubbled' water?
3) What is the pH of tap water left out but not bubbled for 3 days.

I suspect if your results are even close to accurate 2) 3) should be the same and slightly lower than 1) (You would need a calbrated ph probe to check liquid tests not accurate enough)

Hanna Co2 kit is Sodium Hydroxide with phenolpthalein indicator, if your water is not RO with carbonates and fits perfectly theory you don't actually know what your CO2 levels are, any acid or base in the water will cause over/under estimation of the results.

CO2 levels in water depend on elevation and partial pressure of gasses and surface exchange and volume of container. The values range from 0 - 5 ppm in natural open systems.

Quote:
After hooking up the reactor with a whisper 40 air pump and letting it run for 4 hours I found the levels of co2 to be 3-4 ppm.
Turn off airpump and then leave out the same bucket and volume of water out for a few days and then measure again. If the bucket still shows 3 or 4 ppm then 'bubbling' did not increase the CO2 concentration, your tap water just needed to be exposed to air/co2 longer to react with any base in the water.
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post #14 of 20 (permalink) Old 05-28-2019, 08:44 PM
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No amount of aeration can drive the CO2 concentration in your tank above its equilibrium with room air. This turns out to be just 0.5 ppm.

As others have pointed out, natural environments tend to build up much higher concentrations of CO2 than you get from equilibrium with air.
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post #15 of 20 (permalink) Old 05-29-2019, 02:32 AM Thread Starter
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Yeah I kinda already figured out this was not worth doing in an aquarium. That is what this experiment showed to me. When I set out I decided that I wanted to see at least 10 ppm or I would just do pressurized co2. That didn't happen so I will build a diy co2 regulator and go that route. The experiment was still fun and not expensive so it's all good.
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