CO2 for planted tanks: do you actually need it?
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The short answer: no, you do not need pressurised CO2 to keep a healthy planted tank, and most beginners should not start with it. Plenty of hardy plants, anubias, java fern, cryptocoryne, vallisneria and mosses, grow well under moderate light with just a good substrate and liquid fertiliser. CO2 becomes worth considering when you want fast growth, dense carpets, or the demanding red stem plants that simply will not colour up without it. Think of CO2 as an upgrade for a specific goal, not a requirement for a good-looking tank.
What CO2 actually does
Carbon is the nutrient plants need in the largest amount, and in most tanks it is the factor holding growth back. Adding CO2 lets plants use the light and nutrients you are already providing, which is why a CO2-injected tank grows faster and can support species that struggle otherwise. But it only helps if light and nutrients are also in place; add CO2 to a dim, unfertilised tank and little changes.
The three levels of carbon
- None. Perfectly viable. Choose low-demand plants, moderate light, and a regular fertiliser routine from plant fertiliser and additives.
- Liquid carbon. A middle step that gives a modest boost and helps with some algae. Simple to dose with no equipment, though it does not match pressurised CO2 and some plants, such as vallisneria, dislike it.
- Pressurised CO2. The real thing, for high-light, high-growth tanks. A kit like the Fluval Mini Pressurised CO2 Kit suits smaller tanks, delivered through a diffuser such as the Fluval ceramic diffuser.
If you do run CO2, go slow
Too much CO2 will stress or suffocate fish, so increase the rate gradually, watch your fish closely, and turn injection off at night when plants are not photosynthesising. A drop checker and a timed solenoid make this far safer. If that sounds like a lot for your first tank, it is a sign to start without CO2 and add it later.
Match the goal to the effort
Pick your plants and your ambition first, from our live plants collection, then decide on carbon. A calm low-tech tank with easy plants and good lighting is a genuinely fine destination, not a compromise.
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Come and ask us
Fishkeeping goes better when a real person can look at your setup. Come into the store in Lethbridge, call us at 403-380-4506, or send us an email, and someone who keeps fish will help you get it right. Written by the team at Tropical Fish Imports.