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This journal documents my thought process and design decisions for building mini yugang reactors for tanks below 20 gallons/60P.



If this is your first time learning about a yugang reactor, head over to this article:



Yugang CO2 Reactor - A Guide



One of the challenges with the yugang reactor is that they are tough to build for smaller tanks due to material availability. But that issue was solved in this thread below:


Yugang Reactors for Smaller Tanks



After reading the thread above, I thought that the PC cooling reservoir would be a great idea for three reasons:

1. You will be able to disassemble it for cleanup
2. It’s see-through, so you can adjust flow as required, as the flow will decrease over time from filter clog-up. This is sort of important for mini yugangs as significant flow reductions could lead to a slower rate of pH drop. This is discussed in detail later in the journal.
3. Its outflow is off-centre and the cylinder is rotatable as shown in the photo below, thus you can increase or decrease pH drop based on your tank size. This feature is particularly important as the PC cooling reservoirs come in fixed sizes, so the only real way to adjust pH drop is by rotating the cylinder to increase or decrease CO2 absorption.

Challenges with the mini yugang and how to resolve them:

1. Low volume: I have used a 310 mm PC cooling reservoir, with a usable diameter of 40mm. This means that during operation at full capacity the volume of water in the reactor is pretty low; about 185ml. This is a little problematic as the low mass flow rate requirement of the mini yugang coupled with the low volume means that only a small amount of water gets injected with CO2 at any point in time. This leads to the pH drop being very slow for a tank size of 20 gallons. I had designed my yugang for a pH drop of 1.4 and it takes me about 5-6 hours to achieve this. The way to resolve this issue would be by using a reactor with a great length (to be able to afford larger mass flow rates) and a larger volume, but this would mean that you would have a tough time running the reactor in overflow mode as the CO2 gas pocket would have to be very small due to the bigger reactor size. The other solution is to start injecting early like I do. So to conclude, the “rate of pH drop” is dependent on reactor volume, mass flow rate and the size of the fish tank. So keep this in mind if you’re trying to use a mini yugang for tanks bigger than 20 gallons.
2. Usually small volumes of air being purged into the reactor isn’t an issue as yugang points out in his article but if the filter is purging out massive bubbles of air frequently then this most certainly will affect reactor operation. If you own one of the older biomasters one of the issues you’d encounter is the filter purging air into the reactor. This happens in two cases; if you don’t have a bypass or if the tee joint at the bypass is oriented incorrectly. This is why my suggestion would be to install a bypass, as it just gives you more control over the situation. So, what is then the correct tee joint orientation? If you look at the photo below, you’ll see how the bull head of the tee joint is pointing upwards against gravity and that the bypass is connected to the bull head while the reactor inflow is connected to the parallel down-flow. This is key because the bypass being connected to the upwards facing bull head ensures that any bubbles being purged from the filter is not entering the reactor; this happens as bubbles have an affinity to move upwards. In this case, the filter purges air and the bubbles shoot straight into the bypass and out into the tank without entering the reactor and disrupting reactor performance.

I hope the reader will find my experience helpful in designing their own mini yugang. Thank you for reading.

I have this pH tester. You're supposed to keep the probe wet in a specific preservative solution between uses. I have the correct solution. The problem is that it dries out so quickly. I go months between using it, and it dries out. Does anyone have an idea on how to keep it wet? I'm going to put a small piece of sponge in the bottom of the cap and see if that helps.

Started a new tank with the idea of show casing Lagenandra meeboldii which I have not showcased before. Wanted to feature Hygrophila lower Hlaingbwe, but I removed it later as I think it would be too large for this tank.

New substrate, new filter, squeezed filter mulm from the other matured tank, then ran the tank one week day before planting. 100% water change after planting, then 100% water change every other day since then. Dosing 1ml APT3 after water change day, and remineralizing to 5dGH using APT Sky. Trying out the low water column dosing approach for the initial period.

Filter: Oase 250
Lights: Week aqua a430 80%
Substrate: APT Feast

Was going to Journal about startup issues, however, it seems like the tank has already stabilized, skipping diatoms and green dust phase.

Freshly planted for a couple of days:
13/2/2026


Replanted the tops for Myriophyllum roraima, Cut and replanted Rotala blood red to begin building up the bush form. Trimmed old leaves
Foreground seems a bit blocky for now, so I think I'lll move stuff round again. Probably when the BV grows out some more.
Pic on 23/2/2026

Readings at this stage:
Potassium: 2.3ppm
Ammonia: 0.1ppm

reduce water changes to 2 times a week.

Hi all
My Cambomba sometimes develops these roots from the nodes.
Rotala H'ra does it too, but not as aggressively as the Cambomba.
Any ideas why this happens?

This Garlic-centric tank concept popped out on Facebook, wondered what you think about it.

I want to buy a dozen marbeled hatchetfish for my 75 gallon, and everywhere I look they are sold out.

I know a large proportion are wild caught, I would guess after the rainy season with its explosion of breeding.

So is there a season they are more likely on the market?

Ive reorganized the order of my tanks so I can better keep track of them ie. Tank 2 moss tank is now tank 3. This helps in any confusion I had when tracking tanks they are in a sort of order now. Rather than taking time editing my old journal id rather create a new thread. Pics will be current (for the most part) as they are posted. I am not aquascaping. I am just farming.

This is the future home for the announcements when someone obtains an achievement badge. Let the games begin!

Hi all,

First time posting! I was browsing FB and saw someone posted a picture of their tank. Was wondering if anyone could help me ID the plant middle left? Crypt?

Thank you for your help!

Both tanks contain a lot of bucephalandra stems I have recently melted by feeding my caridina tanks with mulberry leaves. I have no idea what the heck happened but all buces melted in those tanks heavily over 3 days with every other plant + shrimp being fine. Don't wanna risk the plants dying so I'm throwing them back into high tech for a few months to recover.

Set Up:
Both tanks uses heavy co2 misting
Horticulture LED lights (dimmed, so probably 25-30 watts?)
Will steadily increase light weekly if I see no issues, max is 40 watts.
Dual sponge filters. (Air bubbles help prevent co2 gassing, also seems to really help stabilize tank, so less algae)
1 Internal filter with an atomizer for misting.

Regime:
All tanks get a 30-50% water change, twice per week.
Micros dosed daily (unless I forget, which happens fairly often.)
Macros Front Loaded and only in new incoming water.

6 Gallon bucket water change:
~350tds (Using seachem equilibrium remineralizer)
~22ppm KNO3, using KNO3 + KH2PO4
~40-50 ppm Potassium due to remineralizer
~4-5GH

Buce Lottery Colors
Lots of buces, various names, collected over the years. A lot of them were ultra rare and I cannot buy them anymore. Most of the ultra rare I probably accidentally killed from trying to grow them in a "no filter, no co2" style tank. Either way, not much color in low tech, will see what lottery colors we pull once they get going with better colors in higher lights + co2.

Both tanks are planted tightly front to back with bucephalandra. Kinda hard to see it all with moss blocking the way, but my view will be your view.

Random Mosses
Some mosses I've collected as well, honestly I grow a lot of them free floating so they kinda look the same. We will find out how they look after I attach them to something.

15 Gallon, very aged sand + pebble tank.

20 Gallon long, aged aquasoil I pulled from an existing caridina tank.


Wanted to take some macro shots, but does anyone know how to take an angle show on the glass without distortion? I have a DSLR long tube lens that works under water but color rendition is really bad.

Why so much moss?
Mostly to help stabilize the tank and to reduce light bleed. Less surface for algae to grow.