The Air Bubbler Tube
The purpose of this kind of tube is to pre-warm and pre-moisten the incoming air. The air enters the bottom of the tube where we glued the tubing into the plug with some aquarium cement to keep it in place.
As the air rises to the higher exit point it moves some of the water along with it and this actually helps the water circulation in the cooler.
In coolers with little room to spare between a tray and the bubbler tube, it is important to let the air exit inside the tube (as seen in the picture below on the right) to prevent the bursting bubbles from spraying water on the incubating tempeh.
This is a picture of the air bubbler tube in the 100 qt Igloo “5 day” cooler.
In this case we let the bubbles and the water out below the water level since there is plenty of room and the tray is 2.5” tall and floats on the water and bursting bubbles will not reach the tempeh.