Many people have the same question: should I buy one of those fancy CO₂ systems, or will a bottle of liquid "EasyCarbo" suffice? Been there, done that – I started with EasyCarbo (convenient and inexpensive), but a few Vallisnerias later, it turned out that wasn't such a smart choice after all. In this article, I'll explain the pros and cons so you don't encounter any surprises.
Gas CO₂ injection provides a stable, powerful supply – ideal for fast-growing aquariums and high-light aquariums. Liquid CO₂ (such as glutaraldehyde products) is cheaper and convenient for low- to medium-tech tanks, but less effective for demanding environments, and some sensitive plants may react poorly to it.
What exactly is the difference between gas CO₂ and liquid CO₂?
- Gas CO₂ injection: reliable, precise, and powerful. Perfect for demanding aquascapes with rapid plant growth. This system adds real CO₂ to the water, increasing the carbon concentration and promoting faster plant growth.
- Liquid CO₂: affordable and easy to use. Especially useful for suppressing algae or in simple tanks without bright lighting. Note: it's not actual CO₂, but a glutaraldehyde solution that indirectly supports plant growth by inhibiting algae.
According to experienced aquascapers on forums like UKAPS and Aquascaping Forum Nederland, liquid CO₂ provides at most 1–2% of the carbon that gas injection can provide. Gas injection is therefore more effective with high light intensities or fast-growing plants.
Why do some plants like Vallisneria react poorly to liquid CO₂?
An important warning: some plants do not tolerate liquid CO₂ well – especially Vallisneria . On aquarium forums, hobbyists report that Vallisneria leaves often "melt" or break off when using glutaraldehyde. The substance attacks the cell walls of sensitive plants and can cause leaf drop.
Community tip: start with half a dose, avoid spot treatment on leaves, and for sensitive species, use a true CO₂ system or a low-tech setup without additives.
How do you choose and use CO₂ in your situation?
- Plants & light levels: Carpet plants or red varieties? Choose gas CO₂. If your plants aren't demanding, liquid CO₂ may suffice.
- Set up the gas system: cylinder → pressure regulator → needle valve → diffuser → drop checker. Start with approximately 1 bubble per second and ensure the drop checker remains lit green.
- Liquid dosage: according to the label (often 1 ml per 40 L per day). Start with half the dosage and observe the plants and fish.
- Monitor plants and algae: Are you experiencing algae growth or "melting" leaves? Adjust the light, nutrients, or CO₂ levels.
What mistakes are often made – and how do you solve them?
- Overdosing on liquid CO₂: especially dangerous for Vallisneria and mosses. Start carefully.
- Running CO₂ at night: a waste of gas – plants don't use CO₂ at night. Set the system on a timer.
- CO₂ without plant food: doesn't work well. Always add nutrients so plants have all the elements they need to grow.
Checklist – what should you definitely check?
- Plant needs: high or low?
- Light level adjusted to CO₂ choice.
- For gas: complete system + drop checker available.
- For liquid: dosing syringe and gentle build-up.
- Good balance between plant food and lighting.
Conclusion – which CO₂ method is right for your tank?
Gas injection is the best choice if you want fast growth, red plants, or a high-tech aquarium. Liquid CO₂ is a great entry-level option for low- or medium-tech tanks, as long as you're careful with sensitive plants like Vallisneria . Not sure what your tank needs? Feel free to send us a message or WhatsApp us at 📲 06-1823814 – we're happy to help!
Read more: How much light does your aquarium need? · Choosing the right substrate .
