The Truth About CO2 And Aquarium Plants In Low-Tech Planted Tanks!
Do aquarium plants actually NEED CO₂? 🤔 This is one of the most misunderstood topics in the aquarium hobby, so let’s clear it up.
First, let’s talk about terminology. When most hobbyists say “CO₂,” they’re usually not talking about carbon dioxide itself — they’re referring to a CO₂ injection system. That distinction matters, because every aquarium already contains CO₂, even if you’ve never added a single bubble from a tank or diffuser.
Personally, I don’t run CO₂ injection on any of my aquariums. Despite that, I’m currently growing close to 70 different varieties of aquatic plants. That’s possible because aquariums naturally produce carbon through multiple biological processes.
Fish, shrimp, snails, and microorganisms all release CO₂ through respiration. Bacteria breaking down fish waste also produce CO₂ as part of the nitrogen cycle. Even plants themselves release CO₂ during respiration, especially at night. All of these natural sources contribute usable carbon to the system.
For many easy — and even some medium-difficulty — aquarium plants, this natural carbon supply is more than enough to stay healthy and grow steadily. Growth will be slower compared to a high-tech CO₂-injected tank, but slower growth isn’t a bad thing. It often means less maintenance, fewer algae issues, and a more stable aquarium overall.
On top of that, many aquatic plants can pull carbon from bicarbonates dissolved in the water. Different plant species use different carbon fixation pathways. Some rely on Rubisco, which is inefficient, while others use PEPC, which is far more effective. Many plants fall somewhere in between.
Plants with more efficient carbon pathways still perform best with injected CO₂, but they absolutely don’t require it to survive.
So here’s the bottom line: A CO₂ injection system can speed up growth and expand your plant options, but most easy aquarium plants thrive just fine using the natural carbon already present in your tank. You don’t need high-tech equipment to have a successful planted aquarium.
