Discus Needs in Brief
Discus originate from the soft, acidic waters of the Amazon. They require:
- A high temperature (28 to 30°C)
- A slightly acidic pH (6.0 to 6.5)
- Very soft water (KH < 3, GH < 6)
- A stable and low-stress environment
CO2: Useful for Plants but Requires Careful Management
CO2 injection is excellent for plants, especially in large planted tanks. It improves photosynthesis and helps maintain a healthy aquatic landscape. But with discus, it demands great care:
- CO2 lowers pH — which can be useful but dangerous if not controlled properly
- Sudden pH fluctuations are poorly tolerated by discus
- Overdosing can cause respiratory stress or even losses
How to Use CO2 Safely with Discus
Here are best practices for successfully combining discus and CO2:
- Use a very fine diffuser or an external reactor for slow and uniform dissolution
- Install a drop checker and aim for a light green color (max 30 mg/L)
- Avoid pH variations greater than 0.2 between morning and evening
- Couple diffusion with a solenoid valve and timer to inject only during the photoperiod
- Regularly measure KH and pH to anticipate any imbalance
When to Avoid CO2 with Discus?
In some cases, it’s better not to inject CO2:
- During stress or medical treatment
- In a breeding tank, where stability is more important than aesthetics
- If regular pH maintenance and testing feels too burdensome
Plants Compatible with Discus (with or without CO2)
Some plants grow very well in warm conditions even without injection:
- Cryptocoryne wendtii
- Echinodorus bleheri
- Anubias barteri
- Vallisneria gigantea
- Bucephalandra (if shading is possible)
Conclusion: CO2 and discus are compatible but require rigorous control of water parameters. The goal is to maintain a stable balance without endangering these magnificent fish.