The 13 mm glass Inline Diffuser is a pollen style inline CO2 diffuser that is placed in the outflow line of the filter or aquarium pump to efficiently diffuse CO2 gas into the aquarium. This placement of the diffuser avoids the need for a diffuser in the aquarium and significantly reduces the visibility of the CO2 injection system in the aquascape. This also allows for more rapid diffusion of CO2 into the system and can allow for more consistent levels and reduce waste of CO2 or overdose of CO2.