These are the most practical diffusers available. In a single piece, you have a check valve, a bubble counter and the diffuser.

CHARACTERISTICS:
•3 functions in one unit: CO2 bubble counter, check valve and diffuser.
•Produces bubbles as small as a mist of CO2, generating maximum possible diffusion on CO2 in the aquarium.
•Undisputable quality and reliability.
•Compact size.
•Easy to install.