Seachem Glass CO2 Inline Diffuser 13mm Global recommendation You can either use cotton

You can either use cotton threat

If you want to avoid this

high range pH

but also carbon

Measure your tank’s length and width in cm

Seachem Glass CO2 Inline Diffuser 13mm Global recommendation You can either use cottonMinimizes the visibility of CO2 equipment in the aquarium Ensures maximum dissolution of CO2 in aquarium water Allows for more consistent dosing of CO2 Compatible with 12 mm ID 16 mm OD hoses 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