This Airline Tubing is the industry standard for aquarium and ponds.
It is made from thick-walled vinyl to prevent collapse.
It is easy to cut with standard scissors. It is translucent, available in 3/16-in, 1/4-in, and 3/8-in. sizes, and is safe for fresh or saltwater. Sold by the foot.
Remember it is always a good idea to have extra on hand.