The Fundamental Role of CO2 in Photosynthesis
To grow, aquatic plants use a process called photosynthesis. This mechanism allows them to capture carbon dioxide (CO2) present in the water to produce vital energy thanks to light. This reaction results in the formation of carbohydrates (the plant’s food) and oxygen molecules, released into the water and essential for fish respiration.
Why Add CO2 to an Aquarium?
Aquarium water naturally contains some CO2, but this level is often insufficient to allow optimal plant growth. Using a CO2 kit, you increase this level, which has several major benefits:
- Improved photosynthesis: plants better assimilate nutrients.
- Accelerated growth: denser foliage, taller plants, faster rooting.
- Better overall health: strong plants limit algae by absorbing nutrients before them.
Demanding Plants and CO2
Certain plant species, such as carpeting plants or those with a red dominance (Rotala, Alternanthera, etc.), are very sensitive to CO2 availability. Without sufficient supply:
- Carpeting plants do not form a dense carpet.
- Red plants lose their bright color and turn greenish or brownish.
CO2 is therefore essential to achieve a professional aesthetic in an aquascaped aquarium.
Natural pH Regulation Thanks to CO2
Another often overlooked advantage of adding CO2 is its effect on the water’s pH. Increasing carbon dioxide concentration naturally lowers pH, which can be useful for:
- Reproducing specific biotopes, such as those in South America (Amazon) or Asia (acidic forest rivers).
- Enhancing comfort for tropical fish that prefer slightly acidic water.
What Equipment is Needed to Inject CO2?
There are different types of CO2 kits for aquariums:
- DIY kit (yeast + sugar): for small budgets and beginners.
- CO2 kit with refillable bottle: precise and durable, ideal for medium to large planted aquariums.
- CO2 kit with disposable bottle: more compact, but less economical in the long run.
The choice depends on the size of your aquarium and the type of plants you maintain.
Conclusion: Why Use CO2 in Aquaristics?
Adding CO2 in a planted aquarium provides your plants with ideal conditions for fast growth, vivid colors, while improving overall oxygenation of the water for your fish. It’s also a powerful tool to stabilize the ecosystem and limit algae.
A well-adjusted CO2 kit is one of the best investments an aquarium enthusiast can make.