CO₂… it sounds like rocket science to many beginners. Do you really need to buy a whole kit, or will your plants manage without it? I remember thinking to myself, "Well, plants breathe naturally, don't they?" Until my tank turned into an algae jungle. In this blog post, I'll explain what CO₂ actually does, and whether it will benefit your aquarium.
Additional CO₂ isn't always necessary. Easy-to-grow plants like Cryptocoryne, Anubias, and Java fern grow perfectly well without it. But if you have bright light and want red stems or a beautiful green carpet, a CO₂ system is almost indispensable. Aim for 20–30 ppm CO₂, let the drop checker turn a nice green, and start slowly at approximately 1 bubble per second.
What exactly is CO₂ in the aquarium?
CO₂ is, along with light and nutrients, one of the three building blocks your plants need. In a low-tech aquarium, plants obtain sufficient carbon from the water itself. However, as soon as you increase the light intensity and try to keep demanding plants, you'll find they thrive much less without additional CO₂. Additional CO₂ works like a turbocharger: faster growth, more compact plants, and less algae—because the plants absorb all the nutrients immediately. But remember: CO₂ isn't a magic anti-algae switch. Without balanced light and nutrients, things will still go in the wrong direction.
How to set up a CO₂ system (step by step)
- Gather your supplies: cylinder, pressure regulator, check valve, hose, bubble counter & diffuser.
- Select the correct bottle: 1–2 kg for containers up to ±75 L; 5–10 kg for larger volumes.
- Assemble and fill: Tighten the regulator, fill your bubble counter and disconnect all hoses.
- Place the diffuser low in the container for maximum bubble dissolution time.
- Connect the solenoid to a timer: CO₂ should only be added in addition to light.
- Start slowly: apply the light at a rate of approximately 1 bubble per second, observing the reaction of plants and fish.
- Check your drop checker: blue = too little, green = just right, yellow = too much CO₂.
Alternatives: liquid CO₂
Don't feel like dealing with all that infrastructure? Fine, then choose liquid CO₂ like EasyCarbo or Excel. These are essentially carbon sources (glutaraldehyde) that you dose daily. For low-tech tanks, this can work perfectly: they give your plants a boost and help prevent algae.
Note: Some plants, such as Vallisneria, sensitive mosses, or shrimp, do not tolerate these liquids well. Always start with slightly below the recommended dose—safety first!
Gas CO₂ vs. liquid CO₂: At a glance
| Aspect | Gas-CO₂ (injection) | Liquid CO₂ (EasyCarbo, Excel) |
|---|---|---|
| Effectiveness | High – immediately available, for demanding plants | Limited – mainly inhibitory, slightly less growth boost |
| Maintenance | Regular check + maintenance required | Daily dosage required |
| Costs | Higher (set + refill) | Low – bottles are affordable |
| Risks | Too much = suffocation; risk of leakage | Overdose dangerous for fish and plants |
| Suitable for | High-tech aquariums | Low-tech baking & beginners |
Common mistakes (and quick fixes)
- Using DIY bottles: unreliable. Fix: choose a pressure-regulated system.
- Incorrect light without CO₂ leads to algae. Fix: reduce light or add CO₂.
- No nutrients with CO₂: deficiencies as a result. Fix: always use good plant food.
- Overdosing on liquid CO₂: dangerous for sensitive plants. Fix it: start with half the dosage.
Checklist
- CO₂ setup complete or liquid CO₂ ready
- Timer keystroke clear: CO₂ runs with light
- Dropchecker set (if gas-CO₂)
- Easy plants ready for a low-tech theme
- Daily check: balance light, nutrition & CO₂
Read more: Successfully keeping aquarium plants , Red aquarium plants .
Conclusion
Low-tech with easy-to-use plants can be fantastic if you're looking for peace and quiet. But dreaming of a jungle with red plants and a dense carpet? Then CO₂ is a must. Not sure what's right for your setup? Send us a message ; we'd be happy to help!
