# Passive CO2/inverted bottle question



## Blue Ridge Reef (Feb 10, 2008)

There's really not a lot to it, you just need a CO2 canister, regulator, and something to hold the bottle in place. I use aquarium magnets and try to position them where they aren't an eyesore. 









It's pretty tucked away at back right of this photo:










I try to fill them every morning before I leave for work and they are usually empty (well, full of water rather than CO2) by the end of the day on these 50 gallon tanks. For what it's worth, it doesn't put nearly the CO2 in the water column that injecting does, I seem to max out around 15- *maybe* 20 PPM. But the difference is noticeable from when I don't do it/run out/get lazy for while, etc.


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## DaveKS (Apr 2, 2019)

If you took that bottle put it’s cap on then cut out the side you would have a much larger co2 to water interface, dilution rate of co2 into water would go up. It’s all reliant on the square in. of co2 gas/water contact area and water current going by a it. 

It’s basically what is called a CO2 bell. Your basically giving water a interface that has 100% co2 gas in contact with it rather than the 3% atmospheric CO2 that it is in contact with at surface of tank water.


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## Blue Ridge Reef (Feb 10, 2008)

DaveKS said:


> If you took that bottle put it’s cap on then cut out the side you would have a much larger co2 to water interface, dilution rate of co2 into water would go up. It’s all reliant on the square in. of co2 gas/water contact area and water current going by a it.
> .


Agree 100%. At the rate it leaves this 24 oz bottle though (out within 6ish hours), I'd have to be home to refill it. How quickly it's used up is the downside of this method, really. I do have a powerhead pointing under the cap in each tank that helps it empty more quickly, it can kinda be seen in the first photo. This was the first CO2 used in an aquarium I'd ever seen in the '90's from my favorite LFS guy from back then. His reasoning was that it would kill your fish if injected too much, but I did it out of having more tanks set up than I had equipment for without having CO2 tubing running all over the floor. I was sketching a design that would incorporate a float switch but at that point might as well just inject.


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## makeme (May 16, 2019)

@Blue Ridge Reef, thank you for the explanation and photos! The plants in your tank certainly appear healthy and lush...I think the majority of them are 'low' light plants, correct? Have you done any experiments in growing the same plants in a different tank without the bottles of CO2? Also, I assume that you fill the bottle from your canister and then place it in the tank; how do you keep it from escaping the bottle during the transfer, or do you just cap it, place it in the tank and then uncap? Would you say this is a cost-effective method or do you run out of CO2 quicker from your canister than if you were using pressurized injection? I'm sorry for so many questions; I'm very intrigued and may consider trying this in one of my non-injected tanks.


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## Blue Ridge Reef (Feb 10, 2008)

It does work, though it's like 50% CO2 injection if you keep them filled -which honestly is the obstacle to this method. It's very easy to get lazy -believe me. I can't count the days I've been rushing out the door and decided to get to them later. Ugh. It's not perfect, but is ballparks better than not using CO2, IMO. As for your question, I don't remove the bottle from the aquarium at all. Just bring the tubing off the CO2 canister to the bottle and ease on the pressure with a needle valve until bottle is full. 

And yeah, two of my 4 tanks that I use these on are all low-light plants, mostly Anubias, Buces, and mosses. The other two have higher lights and more stems, and honestly those aren't ideal for this method. The plants just outgrow the CO2 and ferts I can give them. It isn't perfect, but is about $1000 cheaper than properly setting up pressurized on each of them. And full disclosure, I'm probably going back to pressurized after I get floors refinished and move the two identical Fluval tanks (like the one shown) on opposite corners of the living room. This was what I'd hoped to discuss with that author before the now-closed thread broke down; I never imagined things would go so sideways. But I'll still continue bottles on a couple other tanks, it's SO much better than nothing. And pretty much 0% chance of gassing anything and unlike DIY, it's pretty consistent as long as gas in in the bottle.


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## makeme (May 16, 2019)

@Blue Ridge Reef, thanks again for the information and pointing out the pros and cons. I did read your mention of it in The Thread That Is Now Closed, and it would have been interesting to see you further discuss things with that person...sorry that it had to end in such a hot mess. Such is life and human nature, I guess...Anyway, thanks!


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## DaveKS (Apr 2, 2019)

You should probably watch this guy do it, he just made him a little J hook of rigid airline tube. Actually bells are great paired with a low output yeast reactor type source, all you really need is 1-2 bubbles a minute to keep bell filled.


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## Deanna (Feb 15, 2017)

Here is another in-depth discussion and example of a successful passive approach, provided by @Edward, beginning with this post: https://www.plantedtank.net/forums/11-fertilizers-water-parameters/1269073-ph-drop-review-levels-co2-concentration-3.html#post11040569.

Be sure to read the many posts on that thread that follow. Pictures of the reactor are in later posts.


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## [email protected] (May 22, 2019)

Heh, with this kind of CO2 system you can just blow your breath into the bottle every morning. 😄


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## Edward (Apr 11, 2005)

[email protected] said:


> Heh, with this kind of CO2 system you can just blow your breath into the bottle every morning. 😄


What is your CO2 experience?


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## [email protected] (May 22, 2019)

Edward said:


> What is your CO2 experience?


What is your humor experience? [emoji4]

Sent from my SM-G975U using Tapatalk


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## Edward (Apr 11, 2005)

[email protected] said:


> What is your humor experience? [emoji4]
> 
> Sent from my SM-G975U using Tapatalk


Sent from my SM-G975U using Tapatalk


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## Bettatail (Feb 12, 2009)

DaveKS said:


> You should probably watch this guy do it, he just made him a little J hook of rigid airline tube. Actually bells are great paired with a low output yeast reactor type source, all you really need is 1-2 bubbles a minute to keep bell filled.
> 
> https://youtu.be/VfAJ3ITS3Nw


:grin2:
first 15 seconds into the video I suspect it is ocean aquarium, indeed it is!

the owner look different though, probably he put on a pair of glasses, last time went there was 2011, he used bottles that cut in half and upside down to hold co2 at the time ...


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## [email protected] (May 22, 2019)

The upside down bottle is by far the most efficient CO2 diffuser since no CO2 gets to bubble out. But it doesn't look very attractive, it could work fine in a sump were no one can see it. 

Sent from my SM-G975U using Tapatalk


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## Bettatail (Feb 12, 2009)

@[email protected]

if I have numerous small planted tanks I would probably use the same method, fill the co2 in upsidedown drinking bottles. Simple, steady parameters and low maintenance, but still achieve healthy plant growth. 

If I have a sump, which I do have one, I use pressurized co2 on the planted tank.
I built this co2 system in 2013, and since summer of 2014, I touched it only once(in 2017?) to fill the mineral oil and re-adjust the bubble rate a little bit...

slow co2 injection rate(1 bubble per second) on a 15lb co2 tank, after 6 years the co2 still running...


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## DaveKS (Apr 2, 2019)

It’s kind of up to you how ugly you make it, pop bottle out of trash for free or spend $6 and get nice smoke grey acrylic toothbrush holder and turn it up side down.


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## Econde (Oct 13, 2015)

These would be pretty neat I think.


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## Edward (Apr 11, 2005)

DaveKS said:


> Actually bells are great paired with a low output yeast reactor type source, all you really need is 1-2 bubbles a minute to keep bell filled.
> 
> https://youtu.be/VfAJ3ITS3Nw


 With my design I make side openings to speed up the CO2 gas diffusion. The larger one diffuses 2 bubbles per second. The rate is dependent on flow and mainly on CO2 to water contact surface area.


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## united natures (May 15, 2019)

Okay no joke, but can we actually breath into a bottle and invert it? The average human breath contains about 37mg of CO2.... 

30ppm of CO2 is 0.113g/gallon according to this online converter. For a 10gal tank that's 1.13g of Co2 in the tank.

So one breath and you've outputted ~3% of the total CO2 in the tank! Do this a couple (hundred?) times and you got free, simple, quick and easy CO2!


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## TacitBlues (Aug 4, 2016)

united natures said:


> Okay no joke, but can we actually breath into a bottle and invert it? The average human breath contains about 37mg of CO2....
> 
> 30ppm of CO2 is 0.113g/gallon according to this online converter. For a 10gal tank that's 1.13g of Co2 in the tank.
> 
> So one breath and you've outputted ~3% of the total CO2 in the tank! Do this a couple (hundred?) times and you got free, simple, quick and easy CO2!


It's even better if you breath the same air for a couple minutes, maybe with a baloon, you could really get the concentrations up then!


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## united natures (May 15, 2019)

TacitBlues said:


> It's even better if you breath the same air for a couple minutes, maybe with a baloon, you could really get the concentrations up then!


GENIUS. Why buy Co2 canisters when WE ARE the Co2 canisters! BRB revolutionizing the fish keeping industry.


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## DaveKS (Apr 2, 2019)

Edward said:


> With my design I make side openings to speed up the CO2 gas diffusion. The larger one diffuses 2 bubbles per second. The rate is dependent on flow and mainly on CO2 to water contact surface area.


I use to use these with yeast systems, stainless steel mesh, not only do you get water|CO2 contact on bottom but top side has around 35-45 open space so you get CO2 dissolution from all sides of the bubble surface. Only works with thin bubble layer but you can actually stack them up in a ladder so they spill over into next mesh layer above it. You can get a lot of dissolution in a very small amount of tank space when you start stacking them up. Just be sure you don’t leave any sharp edges exposed in tank.


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## vonguzoff (Dec 19, 2019)

[email protected] said:


> The upside down bottle is by far the most efficient CO2 diffuser since no CO2 gets to bubble out. But it doesn't look very attractive, it could work fine in a sump were no one can see it.
> 
> Sent from my SM-G975U using Tapatalk


It can look attractive if you use this for passive co2 IMO and it is made of glass:


https://www.aliexpress.com/item/32624848796.html

you just need non-return valve
Am i wrong? Maybe I'm wrong....

Cheers from Poland!:nerd:


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