Horizontal CO2 Reactor - Yugang 鱼缸 Reactor

[Yugang]

Hi, I have a question about the overflow. The gases dissolved in the water that accumulate in the bag will be mainly oxygen and nitrogen, gases that are lighter than CO2. In this case, the CO2 is positioned at the bottom of the bag, and consequently, during the overflow operation, the CO2 will be the first to exit, with the consequence that sooner or later the bag will be saturated with other gases and the system will stop working. Is this correct? Thanks.

No, this is not correct at room temperature.

Post in thread 'CO2 Spray Bar - a summary'

Feb 3, 2025

I am posting here to address a common misunderstanding regarding gases at room temperature, where it is thought that the heavier gas CO2 will accumulate at the bottom of a gas pocket. This was mentioned to me in a PM, in the context of the purging of gas in CO2 Spray Bar and Yugang reactor , but I also saw it mentioned at UKAPS.

Indeed, at very low temperatures gas molecules are hardly moving and in this case the heavier gases will accumulate at the bottom while light gases are mostly found in the higher layers.

However, at room temperature molecules move fast and...

• Yugang

• 

 

[Naturescapes_Rocco]

Hi, I have a question about the overflow. The gases dissolved in the water that accumulate in the bag will be mainly oxygen and nitrogen, gases that are lighter than CO2. In this case, the CO2 is positioned at the bottom of the bag, and consequently, during the overflow operation, the CO2 will be the first to exit, with the consequence that sooner or later the bag will be saturated with other gases and the system will stop working. Is this correct?

Edit: I left this thread open on my computer for a few hours and missed Yugang's response to the question. Here's mine:

No. Separation of gases due to weight occurs in spaces/volumes MUCH larger than this. Gases don't form tight "layers" only centimeters high. Can you imagine seeing a small 2" layer of CO2 on the ground outside all the time?

No, this is not occuring in your reactor. When the reactor overflows ("purges"), the gas mixture is being purged -- CO2, N2, O2, all together at once.

By injecting CO2, you ensure that the majority of that gas is CO2. CO2 is also very readily absorbed into water.

 

[Bacherospo]

No, this is not correct at room temperature.

Post in thread 'CO2 Spray Bar - a summary'

Feb 3, 2025

I am posting here to address a common misunderstanding regarding gases at room temperature, where it is thought that the heavier gas CO2 will accumulate at the bottom of a gas pocket. This was mentioned to me in a PM, in the context of the purging of gas in CO2 Spray Bar and Yugang reactor, but I also saw it mentioned at UKAPS.

Indeed, at very low temperatures gas molecules are hardly moving and in this case the heavier gases will accumulate at the bottom while light gases are mostly found in the higher layers.

However, at room temperature molecules move fast and...

• Yugang

• 

My belief, obviously wrong, comes from using the Tetra CO2 Optimat, where on the first day the CO2 was completely absorbed, but gradually other gases filled the bell, no longer allowing the CO2 dosage. I did not calculate the movement in the vertical reactor that favors the mixing of the gases. Thanks for the explanation. Your reactor seems like a truly innovative system to me. Thanks for sharing.

 

[Yugang]

but gradually other gases filled the bell

There is no need for hobbyists to dig deeper in the science, but if you are interested you may want to read

Post in thread 'Horizontal CO2 Reactor - Yugang 鱼缸 Reactor'

Oct 8, 2023

Context

As described earlier, we could operate the reactor in three different ways

• Using a pH/CO2 controller for CO2 injection and stability
• Using a precision CO2 regulator to precisely adjust CO2 injection
• Overflow mode.

Most current users are either using a pH/CO2 controller or a precision CO2 regulator. There will be a reservoir of almost pure CO2 gas in the reactor, and the physics/chemistry of CO2 absorption into the water will be similar to any other reactor that may or may not use CO2 bubbles. As is also the case in bubble reactors, gradually we...

• Yugang

• 
• 

 

[ScaperHaynes]

Hello, connector number 12 is a pneumatic connector, meaning they work in a pressurized system. In this reactor, the CO2 comes out without pressure. Is the seal still guaranteed? Both with the system on, for possible CO2 leaks, and with the system off, for possible water infiltration. Thank you.

Good question! So far I have not had any issues with that fitting. It is a radial seal, meaning that it is more dependent on the o-ring contracting around the tube OD than the pressure. As long as the tubing is stiff enough it shouldn’t be an issue.

Alternatively, you could try a barbed fitting that fits into the ID of the tube instead.

 

[hamfist]

Good question! So far I have not had any issues with that fitting. It is a radial seal, meaning that it is more dependent on the o-ring contracting around the tube OD than the pressure. As long as the tubing is stiff enough it shouldn’t be an issue.

Alternatively, you could try a barbed fitting that fits into the ID of the tube instead.

I'd been avoiding these in my construction. There are occasional horror stories floating around online of these fittings giving out on the seal after a couple of years if the "normal" much more rigid RO filter-type tubing is not used. They are definately convenient though, if they prove reliable.

 

[Yugang]

I figured out the 17.7 ratio for the reactor when I was still into the high CO2 injection rates, now several years ago. Since then I reduced my injection rate in several steps by cutting down the length of my reactor, always using overflow mode.

My reactor is now at a ratio of 44, less than half the injection rate that we would get with the 17.7 ratio.

Using overflow mode I have become very lazy and only check from time to time if everyone is right or that perhaps my CO2 cylinder needs a refill. I am using a drop checker at 1.5 KH as the canary in the coal mine, this would correspond to the lime green at probably 15 ppm. The drop checker is green/yellowish when all is good and something is wrong when it becomes green or even blue.

My estimation is that CO2 is around 15 ppm, and very stable. I am unsure why the recommendation in the hobby is to inject as much CO2 as the fish can tolerate, I hardly notice any compromise at 15 ppm.

I would be interested to know if other hobbyists using overflow mode are mostly at the 17.7 ratio, or also trying other ratios.

 

[Naturescapes_Rocco]

I am unsure why the recommendation in the hobby is to inject as much CO2 as the fish can tolerate, I hardly notice any compromise at 15 ppm.

I would be interested to know if other hobbyists using overflow mode are mostly at the 17.7 ratio, or also trying other ratios.

Do you know what your PAR and water temps are? Plant metabolism rate is determined by light strength primarily, and water temp secondarily.
I'm sure you're growing healthy plants at 15ppm, but I have personal experience that if I have 15ppm CO2 in my tanks with the light strength I run (high light), I get algae because CO2 becomes the limiting nutrient (liebig's law).

If your PAR was, say, 100-200, 15ppm CO2 is probably more than enough!

For me it's not about injecting until fish are uncomfortable -- it's about providing MORE than enough CO2 for my plants. Regular air is ~400+ppm CO2, so you can imagine that CO2 is often the limiting factor in a tank's growth rate... IF the lighting is powerful enough.

 

[Yugang]

Do you know what your PAR and water temps are? Plant metabolism rate is determined by light strength primarily, and water temp secondarily.
I'm sure you're growing healthy plants at 15ppm, but I have personal experience that if I have 15ppm CO2 in my tanks with the light strength I run, I get algae because CO2 is the limiting nutrient (liebig's law).

If your PAR was, say, 100-200, 15ppm CO2 is probably more than enough!

For me it's not about injecting until fish are uncomfortable -- it's about providing MORE than enough CO2 for my plants. Regular air is ~400+ppm CO2, so you can imagine that CO2 is often the limiting factor in a tank's growth rate... IF the lighting is powerful enough.

All fair points @Naturescapes_Rocco, and as you say we cannot rely on one parameter without considering all others like light and temperature.

I guess my point is that experimenting with reducing CO2, until the point where it is clear that results are compromised is interesting and useful. With the reactor we can inject as much CO2 as we want, but the question is if indeed we want to do that.

My tank - in subtropical HK temperature is an issue in the summer, and better now in autumn and winter. I recently upgraded my light (two Weekaqua T90 pro on a 50 gallon tank), and have not yet measured PAR yet.

 

[Gavogr]

Hi All,
Long time reader first time poster. My god what a read.

I have a question if i may.
My tank size is
75cm Tall
45 cm Wide
200 cm Long

So
200x45=9000
9000/17.7=508.47
508.47/???
What's the question marks number, is it the available space i have to fit a reactor?
I have up to 1200cm (4ft) available to me above my sump so wondering what's the best length if that makes sense.


Live in Australia, so was going to see if i can source any clear pipe work closer to home like the amazon links earlier on in the posts.
Would love to get a Stainless steel or even the acrylic version from Aquarocks Colorado but shipping makes it way out of my price range


Any help would be greatly appreciated.
Regards

 

[SingAlongWithTsing]

Hi All,
Long time reader first time poster. My god what a read.

I have a question if i may.
My tank size is
75cm Tall
45 cm Wide
200 cm Long

So
200x45=9000
9000/17.7=508.47
508.47/???
What's the question marks number, is it the available space i have to fit a reactor?
I have up to 1200cm (4ft) available to me above my sump so wondering what's the best length if that makes sense.


Live in Australia, so was going to see if i can source any clear pipe work closer to home like the amazon links earlier on in the posts.
Would love to get a Stainless steel or even the acrylic version from Aquarocks Colorado but shipping makes it way out of my price range


Any help would be greatly appreciated.
Regards

(Tank Surface Area + External Overflow Box Surface Area + External Sump Surface Area) / 17.7 = Diffusion Area Needed
Diffusion Area Needed / Pipe Diameter of your choice = Length of reactor needed

 

[Koan]

5cm / 2" schedule 40 PVC pipe is pretty standard, so 100cm / 39" long pipe (plus length of end fittings) gives 500cm2 max internal surface area, should fit well in the space!

 

[hamfist]

508.47/???
What's the question marks number, is it the available space i have to fit a reactor?
I have up to 1200cm (4ft) available to me above my sump so wondering what's the best length if that makes sense.

THe number you arrive at (508.47) is the water/gas interface surface area needed within the reactor. Don't forget to include your sump's water's surface area as well as the tank's surface area in the total calculation as well. Basically you need to include all water/air surface area where CO2 can be lost by diffusion to know how quickly you'll be needing to put CO2 into the system to compensate to reach your target CO2 levels.

 

[Gavogr]

Actually the sump wasn't included in those numbers so i will have to look at that and add that in aswell.

Thanks for the replies

 

[Minninips]

I'm preparing to build/source Yugang reactors for 2 tanks. I was looking Aqua Rocks Colorado since they have a clean prebuilt option, but I'm wondering if both the small and large are too big (and if that's an issue?). ARC Small = 10.2x37cm, listed as "45cm tank to 89cm tank". ARC Large = 10.2x65cm listed as "90cm tank or more"

The first tank is 75x45x45cm (29.52x17.71x17.71"): 75x45 = 3,375. 3,375/17.7 = 190.68 Diffusion Area. At 10.2cm pipe diameter, I'd need 18.69cm length, which is nearly half the length of the small reactor.

The second tank is 122x50x50cm (48x19.7x19.7"): 122x50 = 6,100. 6,100/17.7 = 344.63 Diffusion Area. At 10.2cm pipe diameter, Id' need 33.79cm length, which is 3.21cm shorter than the length of the small reactor.

Am I missing something here? Maybe I mixed something up in the conversions? ARC's Small Yugang reactor seems too big for both of my setups if I mathed correctly.

 

[Naturescapes_Rocco]

You can simply rotate the reactor to reduce the power.

These calculations are done for running reactors at full power. If the reactor has an offset exit (like the ARC acrylic/stainless), you can rotate the reactor to adjust the power. See this photo:


For your tanks, you could get a small sized reactor and simply rotate it so the exit is positioned higher up in the reactor, to prevent the CO2 pocket from getting too big and gassing your tank. That's why these reactors have offset exits, for this exact reason.

 

[tjcline0]

TL;DR; My reactor wouldn't really provide the co2 levels I was expecting. What's wrong?

I built this reactor for my 120U (120cm x 60cm x 60cm, or 48" x 24" x 24"). Its 21" long using 3" PVC (total pipe length, not extra for fittings). I used the standard area ratio for 1.5 pH drop. I had it inline of an Eheim Pro 3 with a bypass loop to run inline heater and autodoser. I ran the reactor in overflow mode, burping every minute or so. Using both visual drop checker and high resolution pH (+/- 0.01) and KH measurements (+/-0.1 dKH ), the best co2 concentration I could achieve was 15ppm. After from 3-10 hours after co2 on, drop checker was blue-green and co2 was 15ppm as calculated by KH/pH relationship. So this past weekend I built an even bigger one. I doubled the surface area of the new reactor (35" x 4" PVC; its a beast). After 3 hours, the CO2 is bang on 30 ppm (running on overflow mode), exactly double what the previous reactor could do. Did I do something wrong with the first build or miscalculate the sizing? Or does the area ratio need to be adjusted to produce 30ppm in the aquarium?

I run a lot of surface ripples for oxygenation, so I measured the gas exchange component by monitoring pH all night after fully purging the reactor from all gas by tipping it vertically. The gas exchange rate is quite low (0.24 hr^-1), despite my attempts to increase it. I thought it was a bit extreme to think that gas exchange would limit the high end this much, but alas this confirms that its not a huge component.

Anyways, thanks for reading and for your thoughts!



Here is a tank pic from today with 30ppm.

 

[Koan]

Here is a tank pic from today with 30ppm.

Gorgeous!

 

[Naturescapes_Rocco]

Using both visual drop checker

Don't forget, Drop Checkers are delayed by 2+ hours in terms of reading!

and high resolution pH (+/- 0.01) and KH measurements (+/-0.1 dKH), the best co2 concentration I could achieve was 15ppm. After from 3-10 hours after co2 on, drop checker was blue-green and co2 was 15ppm as calculated by KH/pH relationship.

To be honest, evaluating CO2 levels via pH/KH will always be somewhat inaccurate, or occasionally very inaccurate for reasons I've gone into in many previous posts! Those charts are not good, and there are all sorts of issues with measuring KH and pH, too. Get a Hanna CO2 checker or any CO2 titration test kit and you'll have a much more accurate reading.

So this past weekend I built an even bigger one. I doubled the surface area of the new reactor (35" x 4" PVC; its a beast). After 3 hours, the CO2 is bang on 30 ppm (running on overflow mode), exactly double what the previous reactor could do. Did I do something wrong with the first build or miscalculate the sizing? Or does the area ratio need to be adjusted to produce 30ppm in the aquarium?

There are a lot of factors that could affect this, including design, flow, surface agitation/degassing rate, etc, but I've found that the 1/17 ratio was always underpowered for my tanks. I want ~30-40ppm CO2 in my tanks for the entire photoperiod, and I find that 1/17 just doesn't cut it!

View attachment 13041

Great tank, you know plenty of what you're doing. Get a Hanna CO2 test kit, a 10mL luer lock syringe and some permanently reuseable stainless steel hobby needles to take 10mL water samples, and you'll never need to do any more guessing. I genuinely consider these test kits requirements for dialing in CO2 properly, IMO.

 

[tjcline0]

Don't forget, Drop Checkers are delayed by 2+ hours in terms of reading!

To be honest, evaluating CO2 levels via pH/KH will always be somewhat inaccurate, or occasionally very inaccurate for reasons I've gone into in many previous posts! Those charts are not good, and there are all sorts of issues with measuring KH and pH, too. Get a Hanna CO2 checker or any CO2 titration test kit and you'll have a much more accurate reading.

There are a lot of factors that could affect this, including design, flow, surface agitation/degassing rate, etc, but I've found that the 1/17 ratio was always underpowered for my tanks. I want ~30-40ppm CO2 in my tanks for the entire photoperiod, and I find that 1/17 just doesn't cut it!

Great tank, you know plenty of what you're doing. Get a Hanna CO2 test kit, a 10mL luer lock syringe and some permanently reuseable stainless steel hobby needles to take 10mL water samples, and you'll never need to do any more guessing. I genuinely consider these test kits requirements for dialing in CO2 properly, IMO.

Thanks for the input. I'll order a CO2 test kit just for curiosity and report back. Yeah, drop checkers are good indicators if it's been long enough. I read mine at the beginning and end of the photoperiod, and they are always the same because I usually start my CO2 4-5 hours before lights on for a tank this big. They are a reliable indicator when used properly, but not precise.

I somewhat agree on ph/kh when used by most test kits/hobbyists. I'm using a laboratory pH meter and accurate kH tests. I also run remineralized RO and do a lot of water changes so there is really nothing affecting pH (e.g. dissolved organic carbon) or acid-base reactions other than these two components. So I would argue that these estimates are quite accurate and also in line with my expectations and visual assessments. I got a massive outbreak of BBA when I installed my first reactor and was only getting 15ppm under the same lighting (switching from a previous vertical mixing style reactor which was producing 30 ppm).

I also have measured pH drop from degassed aquarium water (ran a bubbler on it until pH stabilized), and I need this larger reactor to get anywhere north of 0.8-0.9 ppm drop.

Maybe we can figure out what elements of design, flow, and surface agitation are limiting, such that better guidance on sizing could be provided.
Some contributions here suggest that flow rate doesn't matter much, and I would agree with that based on my own observations. I can basically close off the reactor or send all the filter flow through it, and I get very similar CO2 when it's running in overflow mode regardless of flow. The adjustable ones are probably the way to go, but with DIY builds you have to build a version, see if it produces enough CO2, and if not built another (and another if you still are not where you are).