DIY CO2: Citric Acid + Baking Soda for Aquarium

DIY CO2 for Aquarium - Citric Acid + Baking Soda Method

CO2 is a valuable ally to boost plant growth in a planted aquarium. If you have a small budget or enjoy DIY projects, the homemade CO2 system based on citric acid and baking soda is a simple, economical, and effective solution. Here is a step-by-step tutorial.

Principle of the DIY CO2 System

The reaction between citric acid and baking soda produces carbon dioxide (CO2) which will be injected into the aquarium via tubing and a diffuser.

Mild, controllable reaction
No yeast or fermentation involved
Stable production for several weeks

Required Materials

2 plastic bottles (1L or 1.5L)
1 CO2 tubing with connectors
1 check valve
1 CO2 diffuser adapted to the tank volume
Citric acid powder (150 g)
Food-grade baking soda (200 g)
Teflon tape or hot glue gun for sealing

Assembly Steps

Fill the first bottle with 150 g citric acid + 300 ml warm water.
In the second bottle, add 200 g baking soda + 300 ml water.
Connect the two bottles with a sealed tube (acid bottle ➝ baking soda bottle).
A second tube goes from the baking soda bottle to the aquarium (via a check valve and diffuser).
Seal all caps well (hot glue or Teflon tape).
Pressing the acid bottle starts the reaction (visible bubbles in the bubble counter if added).

Usage Tips

Use a small bubble counter to visualize the flow.
Diffuse CO2 only during the photoperiod (using a valve or clamp).
Add a pH or CO2 test kit to monitor concentration (target: 20-25 mg/L).
Refill every 2 to 3 weeks depending on your aquarium volume.

Advantages and Limitations

Advantages: very economical, easy to set up, perfect for small tanks (nano).
Limitations: requires some maintenance, intermittent production if poorly adjusted, not suitable for large aquariums (>100L).

Conclusion

The DIY CO2 system based on citric acid and baking soda is a simple and effective way to start CO2 injection in your aquarium without breaking the bank. This DIY system is perfect for testing the impact of CO2 on your plants while maintaining full control of your setup.