Top Hat Gromet 13 mm, a rubber gasget with 13 mm Barb joiner for hose connection
Plastic 13 mm I-connector for pipe with an inside diameter of approx. 11-13 mm
The I-connector fits Ø 15 mm silicone tube and 16 mm main tube.
Drill a hole ( ~15 mm) in the water tank side. Insert a gasket into the hole on the outside of the tank and finally an I-connector to which the hose is connected.