Introduction to CO2 Supplementation for Aquatic Plants | From Equipment Selection to Setup

Adding CO2 (carbon dioxide) to your aquatic plant tank is an extremely effective method for growing beautiful and healthy plants. CO2 supplementation activates photosynthesis in aquatic plants, significantly improving their growth rate and coloration. This article provides detailed explanations from the basics of CO2 supplementation to equipment selection and appropriate supplementation levels.

Why CO2 Supplementation is Necessary

Aquatic plants create nutrients using light, water, and CO2 during photosynthesis. While natural rivers and lakes contain sufficient dissolved CO2, in the closed environment of an aquarium CO2 tends to be severely deficient.

The benefits of CO2 supplementation include the following:

• Promotes aquatic plant growth: Photosynthesis becomes more active, and leaf development speeds up
• Improved coloration: Red aquatic plants more readily display vibrant red colors with CO2 supplementation
• Algae suppression: Healthy aquatic plants absorb nutrients efficiently, reducing the nutrients available for algae growth
• Beautiful bubbles: Oxygen bubbles produced during photosynthesis create a dreamlike appearance in the tank

In particular, stem plants and foreground plants such as Glossostigma, Pearl Grass, and Rotala cannot display their true beauty without CO2 supplementation.

Comparison of Pressurized Cylinder, Fermentation, and Chemical Reaction Methods

There are several methods for CO2 supplementation. Understand the characteristics of each and choose the method that works best for you.

1. Pressurized Cylinder Method (Mid-sized and Small Cylinders) - Advantages: Stable supplementation rate, fine adjustments possible, good cost-effectiveness over time - Disadvantages: High initial cost (regulator, solenoid valve, etc.) - Recommended for: Those wanting to grow aquatic plants seriously, tanks 60cm or larger

2. Fermentation Method (Yeast-based) - Advantages: Very low initial cost (can be homemade with plastic bottles) - Disadvantages: Difficult to adjust supplementation rate, affected by temperature, requires regular solution changes - Recommended for: Those wanting to try it out, small tanks (30cm or smaller)

3. Chemical Reaction Method (Citric Acid + Baking Soda) - Advantages: More stable than fermentation method, can reduce costs with DIY approach - Disadvantages: Cannot make precise adjustments like the pressurized cylinder method - Recommended for: Those considering stepping up from the fermentation method

For beginners, we recommend first experiencing the effects with the fermentation method and then stepping up to the pressurized cylinder method.

How to Choose a Diffuser

Choosing the right diffuser to efficiently dissolve CO2 into the water is also important.

• Ceramic diffuser: Produces fine bubbles with high dissolution efficiency. Most common and easy to use
• Inline diffuser: Connects to external filter tubing. Keeps the tank looking clean but requires an external filter
• Integrated bubble counter type: Easy to visually confirm supplementation rate. Especially recommended for beginners
• CO2 mixer (reactor): Highest dissolution efficiency but designed for larger tanks

Select one appropriate for your tank size and install it in a location with water flow to maximize dissolution efficiency.

Appropriate Supplementation Rate and Measurement

The appropriate CO2 supplementation rate varies depending on tank size. Here are the guidelines:

• 30cm tank (approx. 13L): About 1 bubble per second
• 45cm tank (approx. 30L): 1-2 bubbles per second
• 60cm tank (approx. 57L): 2-3 bubbles per second
• 90cm tank (approx. 157L): 4-5 bubbles per second

A drop checker is convenient for confirming CO2 concentration. Simply place it in the tank and the reagent color changes according to CO2 concentration.

• Blue: CO2 deficiency (more supplementation needed)
• Green: Appropriate range (approx. 20-30mg/L)
• Yellow: Excess (dangerous for livestock, reduce supplementation immediately)

Supplementation Timing and Precautions

Here are the key points for effective CO2 supplementation:

1. Start 1 hour before lights turn on: To ensure sufficient CO2 concentration when lights turn on
2. Stop when lights turn off: Photosynthesis does not occur in darkness, and excess CO2 can harm livestock
3. Automate with solenoid valve: Using a timer and solenoid valve together enables automatic ON/OFF switching
4. Use with aeration: Perform aeration only at night to replenish oxygen
5. Observe livestock: If fish or shrimp gather at the water surface, it's a sign of excess CO2. Stop supplementation immediately and perform aeration

At Grower Choku, you can purchase not only aquatic plants but also receive advice from growers with extensive knowledge of CO2 supplementation. The ability to directly consult with growers about aquatic plants suited to your growing environment is a unique strength of Grower Choku. Please feel free to take advantage of this service.

Balance Between CO2 Supplementation and Aquatic Plant Growth

To maximize the effects of CO2 supplementation, balance with lighting and fertilizer is important. Even if you increase only CO2, if lighting is weak, aquatic plants cannot photosynthesize actively and excess CO2 will simply remain dissolved in the water. Conversely, if lighting is strong but CO2 is deficient, aquatic plants cannot photosynthesize adequately, causing stress and allowing algae to dominate. The ideal balance is a three-pronged approach: gradually adjusting CO2 supplementation to match lighting intensity and supplementing with liquid fertilizer for nutrients. Evidence of active aquatic plant photosynthesis is the fine bubbles (oxygen bubbles) rising from leaf surfaces. An environment with abundant such bubbles indicates proper balance. When performing CO2 supplementation for the first time, we recommend first experiencing the effects with the fermentation method and then stepping up to the mid-sized cylinder method—this route has fewer failures. Start with modest supplementation and gradually increase while observing the condition of your aquatic plants and livestock.

Frequently Asked Questions (FAQ)

Q. Does CO2 supplementation have negative effects on fish?

A. No problem if done in appropriate amounts. It's safe as long as the drop checker maintains the green range. However, excessive supplementation can cause oxygen depletion. If fish are gasping at the water surface, stop supplementation immediately and perform aeration.

Q. Is CO2 supplementation necessary for small tanks?

A. It depends on the aquatic plants you're growing. It's not necessary for low-light plants such as Anubias and Willow Moss. If you want to create a foreground plant carpet, fermentation-based CO2 is sufficient for good results. Small tanks have the advantage that a small amount of supplementation can achieve adequate CO2 concentration because of the limited water volume.

Maintenance of CO2 Supplementation Equipment

CO2 equipment requires regular maintenance. Wash the diffuser by soaking it in bleach every 1-2 months to clear clogging and restore fine bubble production. The water in the bubble counter evaporates, so refill it regularly. Check the solenoid valve's operation once a year, and consider replacing it if it makes unusual noises.