DIY CO2 for Planted Tanks — Yeast vs Citric Acid Methods

CO2 supplementation is the most effective way to promote photosynthesis in aquatic plants and dramatically improve growth. However, assembling professional equipment like pressurized CO2 cylinders and regulators involves high initial costs. This is where DIY CO2 systems, made from readily available materials, come into focus. Here we explain the two most popular DIY methods in detail.

Yeast Fermentation CO2: How It Works and How to Build It

The simplest DIY CO2 method is the yeast fermentation system.

Basic Principle When yeast is added to sugar water, the fermentation process produces alcohol and CO2. This CO2 is channeled into the aquarium through tubing. It works on the same principle as bread making and is highly safe.

Required Materials A PET bottle (500ml-1L), air tubing, check valve, diffuser, 100g sugar, 1g dry yeast, 400ml water, and gelatin (optional). Total cost is around 1000 yen to get started.

Building Instructions The gelatin method is recommended. Soak 5g of gelatin in 100ml water, then heat 100g sugar with 200ml water to dissolve. Add the gelatin and mix, pour into the PET bottle, and refrigerate until set. Once solidified, add 100ml lukewarm water and 1g dry yeast, connect tubing to the cap, and seal. Setting the sugar with gelatin stabilizes the fermentation speed and allows CO2 production to continue for an extended period.

Duration Depending on temperature, CO2 will continue to be produced for approximately 2-4 weeks. Production is faster in summer (shorter duration) and slower in winter.

Chemical Reaction CO2: How It Works and How to Build It

For more stable output than fermentation, the chemical reaction method is recommended.

Basic Principle Citric acid and baking soda react to generate CO2. Two PET bottles are connected with tubing, one containing citric acid solution and the other baking soda. By gradually feeding citric acid solution into the baking soda bottle, stable CO2 generation is achieved.

Required Materials Two carbonated beverage PET bottles (pressure-resistant), connecting tubing, check valve, speed controller, diffuser, 200g citric acid, and 200g baking soda. Total cost is approximately 2000-3000 yen.

Advantages Compared to fermentation, output is more stable, and the speed controller allows fine adjustment of CO2 dosing. It is also less affected by temperature.

Precautions Since pressure builds up inside the bottles, always use pressure-resistant bottles designed for carbonated beverages. Regular PET bottles risk bursting.

Pros and Cons of DIY CO2

Here is a comparison with pressurized cylinder systems.

Advantages The dramatically lower initial cost is the biggest appeal. Materials can be found at supermarkets and 100-yen shops, and for small tanks, sufficient CO2 output can be achieved.

Disadvantages The inability to stop CO2 at night, difficulty in precise output control, and insufficient output for large tanks are the main drawbacks. Regular material replacement also adds ongoing effort. For those aiming for a serious planted tank, consider upgrading to a pressurized system eventually.

Safe Installation and Operation Tips

Here are important points for safely operating DIY CO2.

A check valve is essential If aquarium water flows back into the CO2 generator, the contents will flood into the tank causing a disaster. Always install a check valve.

Mind the placement Since fermentation speeds up at higher temperatures, avoid placing it where tank lighting generates heat. Installing in a location with stable room temperature is ideal.

Use with aeration Since DIY CO2 continues adding CO2 at night, we recommend turning on aeration via timer simultaneously with lights off. This prevents oxygen depletion from excess CO2 at night.

Aquatic Plants That Grow Well with DIY CO2

There are plenty of aquatic plants that thrive even with the moderate CO2 levels provided by DIY systems.

Recommended species Rotala rotundifolia, Pearlweed, Green Rotala, and Water Wisteria. These species show clearly noticeable growth improvement even with small amounts of CO2.

More challenging species Foreground plants like Dwarf Baby Tears and Glossostigma have high CO2 demands and may not get enough from DIY systems. If attempting these, ensure all other conditions are optimized.

DIY CO2 is the perfect first step into planted tank cultivation. On Botachoku, some growers specialize in selling aquatic plants that are easy to grow even for CO2 beginners. Consulting about CO2 supplementation at the time of purchase will get you specific advice tailored to your setup.