Aquascape® 300 Watt Pond De-Icer EPIC The recommended tubing sizes are

The recommended tubing sizes are 1/2" or 5/8"

see the attached Technical Information Sheet

Prop 65 Warning  Instructions   Installation Tips Warranty

the air switch may be in the wrong position

Aquascape® 300 Watt Pond De-Icer EPIC The recommended tubing sizes areThe Aquascape 300 Watt Pond De Icer is ideal for keeping a small hole in the ice during cold winter months, and ensures proper gas exchange, helping keep fish alive throughout the winter. Maintaining this opening is paramount for the safety of your fish. The De Icer is energy efficient and its stainless steel construction will prevent corrosion and cracking throughout the year, providing years of trouble free operation. A built in LED light will