Why Do Some Plants Need CO₂?
CO₂ is essential for photosynthesis. While some undemanding plants make do with naturally dissolved CO₂, others require active injection to:
- Reach their optimal growth
- Maintain their compact form or vivid color
- Avoid melting or visible deficiencies
Carpet Plants: Demanding but Spectacular
These are the most sensitive to CO₂ deficiency. Without injection, they stagnate or quickly perish. They create a natural green carpet at the front of the tank.
- Hemianthus callitrichoides (HC Cuba)
- Eleocharis parvula / acicularis (mini hairgrass)
- Glossostigma elatinoides
- Monte Carlo (Micranthemum tweediei)
Red Plants: CO₂ Essential for Their Color
Red plants require strong lighting and CO₂ to express their pigmentation. Without these, they become dull or turn green.
- Rotala rotundifolia (red variety)
- Alternanthera reineckii
- Ludwigia repens Rubin
- Ammania gracilis
Fast-Growing, Thin-Stemmed Plants
These plants grow tall and consume many nutrients, especially CO₂. They are ideal for dynamic backgrounds.
- Pogostemon stellatus
- Rotala wallichii
- Limnophila aromatica
- Myriophyllum mattogrossense
Sensitive Plants Without CO₂ Injection
Without CO₂, these plants:
- Drastically slow their growth
- Become prone to algae or yellowing
- May melt (disintegrate) within weeks
Conclusion: If you want a dense, aesthetic, and lively planted aquarium, CO₂ injection is essential to maintain certain varieties. It unlocks the full visual potential of the most spectacular aquatic plants.
See our guide for a CO₂ system with a fire extinguisher for your plants