The CO2 diffuser is the main component of delivering your CO2 into the aquarium. The CO2 diffuser is usually connected to a bubble counter with CO2 tubing & is controlled by a needle valve for precise delivery of CO2. The main purpose of the diffuser is to break down the large bubbles into tiny bubbles from the CO2 regulator to dissolve in the water. When you buy tubing for connecting your diffuser to the regulator make sure it is CO2 proof as it is designed to fit snug on the bubble counter to prevent leaking. There are 3 main types of diffusers for dissolving CO2 into aquaria(Diffuser, Inline Diffuser, Reactor). Below you will find the necessary components for dissolving CO2 into your aquarium.