CO2 System and Accessories

Plants need carbon to grow, but aquarium water usually holds little of it, especially under strong light. Added CO2 speeds up growth, helps carpeting plants grow dense and gives red plants their colour. In a low-light tank with anubias and mosses, CO2 is usually not needed.

A system consists of a regulator, bubble counter, check valve, CO2-proof tubing and a diffuser or reactor. The check valve stops water from flowing back into the regulator. Ordinary silicone tubing lets the gas escape through its walls, so use CO2-proof tubing. Ready-made kits for smaller aquariums come with parts that already fit together.

Switch the CO2 on about an hour before the lights come on and off an hour before they go out. The most common mistake is raising the dose too quickly: increase the bubble rate gradually over several days and watch how the fish behave.