Pressurised CO2 vs liquid carbon
The question every planted-tank beginner asks. Pressurised CO2 is the real deal for lush growth; liquid carbon is the cheap, simple bottle. Here's the honest difference — and when each makes sense.
The quick verdict
If you want demanding plants, carpets and fast, pearling growth, pressurised CO2 — a regulator like the CO2Art Pro-SE on a timer with a drop checker — is the answer, and nothing else matches it. If you keep easy plants and just want a low-fuss boost, liquid carbon is a legitimate, cheap starting point.
| Pressurised CO2 | Liquid carbon | |
|---|---|---|
| Plant growth | Excellent (all plants) | Modest (easy/medium plants) |
| Upfront cost | Higher (kit + cylinder) | Low (a bottle) |
| Ongoing effort | Refill cylinder, set timer | Dose daily from bottle |
| Carpets / high-tech | Yes | No |
| Risk | Overdose if unmonitored | Harms some plants/shrimp if overdosed |
| Best for | Serious planted tanks | Low-tech, easy plants |
Results vs simplicity
Pressurised CO2 delivers a steady, adjustable supply of the exact thing plants are usually starved of — the result is faster growth, deeper colour and carpets that actually fill in. Liquid carbon supplies a bioavailable carbon source from a bottle: genuinely helpful for easy plants and a bit of algae control, but limited, and disliked by a few species. It's a supplement, not a system.
Which should you choose?
Our pick
Serious about a planted tank? Go pressurised CO2 — see our CO2 systems and the CO2Art Pro-SE. Just want an easy low-tech boost? Liquid carbon is a fine, cheap start you can always upgrade from later.
Frequently asked questions
Is liquid carbon as good as pressurised CO2?
No — and it is honest to say so. Liquid carbon (like Seachem Flourish Excel) is a useful supplement that helps easy and medium plants and suppresses some algae, but it is not a substitute for the real thing. For demanding carpets, fast growth and the classic pearling planted tank, pressurised CO2 is in another league.
When is liquid carbon the right choice?
For low-tech tanks with easy plants where you do not want a CO2 cylinder, or as a stopgap while you set up a pressurised system. It is cheap, simple and dose-from-a-bottle easy. Note that some plants (notably Vallisneria and some mosses) can react badly to it, so dose conservatively.
Is liquid carbon safe for fish and shrimp?
At the recommended dose it is generally safe, but overdosing can harm sensitive fish, shrimp and certain plants. Follow the bottle, start low, and never pour large amounts into a small tank. Pressurised CO2 is also safe when a drop checker keeps you in the green range.
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