Using a bell siphon is an easy way to drain a grow-bed in an aquaponic or hydroponic system. The idea is 
that in an ebb and flow system, you have a tank of fertilizer (for aquaponics its a fish tank) and a grow bed full of plants. You then pump the fertilizer into the grow-bed and the plants eat. The problem is that you cannot generally have the plant roots submerged in water all the time as the roots will rot. And you have to have a means to empty the tank so it does not overflow.
A bell siphon solves this problem very simply, with the added benefit of working without additional energy input. This is the coolest part about this system. A bell siphon works solely on the physics principles of atmospheric pressure and vacuums!
For more information on exactly how a bell siphon works, as well as how they’re constructed, check out this handy guide provided by the University of Hawaii: University of Hawaii Bell Siphon Guide
And for some of the supplies necessary to build this project, check out our online store:
Uniseal Grommets
Tubing
Expanded Clay Pebbles
Reservoirs