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Contents:
Benefits of Yugang reactor
Calculate the reactor dimensions
Overflow mode, regulator mode, pH/CO2 controller
Overflow mode, step by step instruction
Regulator mode, pH/CO2 controller mode, step by...
For anyone else struggling to find where to buy clear pipe and the appropriate fittings for building one of these Yugang reactors DIY, hopefully this will save you all some time and work.
I'll be making a journal at some point about this build that this belongs to, but no commercially made reactors would even remotely fit in my stand so I decided to build this per the guidance of
@Jeff Miotke .
Please make sure to select a pipe length appropriate for your tank per:
Yugang CO2 Reactor - A Guide
As per Yugang's guide, clear pipe isn't strictly necessary, but I find it helpful...
I have an old "vertical" CO2 reactor lying around (next to my UNS 90B, an upcoming project!):

This old reactor works by making a "vortex/spiral" of water flowing in due to a 90-degree elbow piece, with a CO2 gas pocket at the top that is in contact/agitation with the vortex. A long clear return tube takes the CO2-enriched water from the bottom of the vessel back to the aquarium while leaving the CO2 pocket at the top of the vessel.
It is heavily dependent on flow, super loud, and seriously reduced my filter's flow rate (180-degree water direction inside doesn't help!). It wasn't...
If you have questions, post them! We love to help out here, I particularly love helping with reactors and CO2.
Getting mine dialied in has changed my life!
Thank you both so much.
Backstory of my journey in this hobby for those interested:
I got into this hobby after my girlfriend won a 3.5 gallon in a white elephant gift exchange of all things. She surprised me with it when she got home, and the part that I didn't expect most of all was that the person included a live betta lmao. I immediately wanted to know everything necessary in order to give him a great quality of life, which led me to buy a Fluval Spec V (5-gallon long) that I planted and put driftwood in.
Then some time went by before a relative told me he found a tank on the side of the road or something, so my girlfriend and I set up and planted this 20-gallon tall tank with the intention of having a betta sorority. Well, that was too stressful; the plants hadn't grown in nearly enough to establish territories, they were varying ages, etc. It was a disaster. We didn't lose any of them, but neither of us wanted the tank to be such a source of stress when it was supposed to be the opposite. We ended up keeping one of them, giving another to a trustworthy friend, and the rest we were able to surrender to my mom and pap LFS for store credit. After this, we felt the tank was too bare, so we got an albino bristlenose pleco, and then I discovered kuhli loaches, so I bought as many as possible. Also, sidenote, this tank was being filtered by two HOB filters, both rated for multiple times the tank's volume.
I experimented with CO2 for the first time on this tank, using a paintball tank and a ceramic diffuser with a drop checker. I couldn't quite find a balance, though, and got absolutely overwhelmed with algae, so I stopped running CO2 on the tank, which I'm pretty sure stunted the plants in this tank, and they have never quite bounced back from that, unfortunately. I'm not certain if that's a scientifically backed phenomenon, or if they are just growing extremely slowly now without CO2, and I simply got used to the insane growth from running CO2. Regardless, I bought a weekaqua light for this tank just before I decided to stop running CO2 on it, so now it's only running at 50% because I believe it's way too powerful to run at 100% without CO2. Fast forward, and the current stocking in the tank is that same bristlenose, along with, I believe, 3 different varieties of kuhli loaches (the all brown ones, tiny striped, and giant striped). Since the betta we kept unfortunately passed after only a year and some change, we decided that the beauty of bettas is not worth the heartbreak as a result of the genetic fragility from breeding malpractices. So I recently picked up like 25 chili rasboras and the same number of CPDs because I have had terrible luck with them from my LFS, and experience overwhelming losses with them specifically.
Besides that, I also started up a 40g breeder in February that I'm absolutely in love with. I found a solid deal on Facebook Marketplace for the tank and stand, and he ended up letting me have a fluval 306, which I put on the 20g, and an fx6 which is now on the 40g! It's an asian biotope with 10 glass catfish, 15 gold ring danios, 6 sparkling gouramis, and two different bristlenose plecos (L262 & L129) which never come out lmao.