Standard hose sizes for fish keeping hobby.
Oxygen Hose
Internal diameter 4-4.5 mm (3/16″)
External diameter 5-6.5 mm
Material PVC
Carbon Dioxide Hose (CO2)
Internal diameter 4-4.5 mm (3/16″)
External diameter 5-6.5 mm
Material PVC
External Filter Canister Hose
Sizes depend on your filter sizes.
8/12 mm
12/16 mm
16/22 mm
18/24 mm
Material Plastic