Journal Mini Yugang - My experience

[Scaper26]

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.