Yeast Reactor Assembly
The most basic model involves using common parts and ingredients. There are numerous variations but the following steps describe a basic reactor assembly.
1. Make a hole in the lid that you can just fit some aquarium airline through (about 6mm wide)
2. Attach the lid to the airline. You can use some silicone sealant or other convenient adhesive.
3. Dissolve two teaspoons of sugar & 1 teaspoon of brewer's yeast in a litre of warm water.
4. Place liquid in reactor chamber.
5. Place loose tubing end into aquarium.
Yeast Reactor Maintenance
Carbon dioxide will be produced until the yeast runs out of food or is poisoned by the waste alcohol produced. Top up the reactor with a teaspoon of sugar as required then overhaul the entire unit every few weeks. Fermentation yeasts will tend to last longer than brewer's yeast because of their higher alcohol tolerance.
Yeast Reactor Optimiziation
Once you have built a yeast reactor you can optimize it and your aquarium for maximum effect. Carbon dioxide is less stable than Oxygen when dissolved in water and tends to exit easier. It’s one thing to make the CO2 but you need to help keep it in the tank.
The type of filtration you use is an important choice. Non bubbling types that sit well below the waterline are best. Some water movement is useful to circulate nutrients but the minimum should be aimed for. Internal power filters are a good variety as they meet all of these criteria.
To help the CO2 enter the aquarium a number of strategies can improve diffusion. By connecting an air stone to the airline tubing smaller bubbles are created. This vastly extends the surface area of the gas allowing for improved absorption. Caution should be used with this method by cleaning the air stone regularly to avoid pressure back up.
A diffusion bell can also be positioned to catch the bubbles of Carbon Dioxide. This is essentially a reservoir for the produced gas that sits inside the aquarium. The Carbon Dioxide remains pressed to the water instead of entering the atmosphere.
Alternately the CO2 line can be connected to the small internal power filter you will have chosen for your aquarium. Some of these filtration devices are available with an inlet for air that can be used or this purpose. Commercial devices designed for diffusing CO2 are also on the market. By running the CO2 through the filter's impellor along with the water you can mix the gas into the liquid quite efficiently.
DIY Reactor Limitations & Problems
This yeast method has its drawbacks. The Carbon Dioxide cannot be regulated to such a fine degree as a CO2 cylinder and injection needle set up. Carbon dioxide levels can fluctuate as the yeast culture reaches its production peak then levels off. This can upset the saturation level in the water. In extreme situations the unit can explode spewing yeasty alcohol all over your fish room. The culture can send froth up the airline into the fish tank if too much sugar is added.
Some further additions to increase safety are:
Airline check valve. One of these can stop any potential water backflow into your reactor. This might be of importance if you have a heater that becomes exposed by the lost water,
A second vessel set up to catch any yeast mixture overflow. By linking two bottles together the empty bottle can act as a liquid reservoir.
Excess pressure release valve. Should anything obstruct the Carbon Dioxide outlet this will contain the problem.
PH or CO2 electronic meter with alarm. Carbon Dioxide dissolves into the water as carbonic acid and the PH drops as a result. The acidity your aquarium plants and fish will tolerate will be the limit of how much CO2 you can safely add. Remember to introduce all PH changes gradually.
Summary
For some aquarium enthusiasts, getting away with the minimum cost and equipment can be as satisfying as the final result. For growing aquarium plants a yeast reactor is an ideal DIY project
Plant Carbon Dioxide Aquarium Plants
