So we can get the best out of this experiment this system will incorporate three different types of grow beds.
1. Ebb and Flow
An ebb and flow or flood and drain grow bed is filled with 20mm gravel to a depth of 300mm. an auto siphon is set up so that when the grow bed fills to a level of 250mm the siphon kicks in and the grow bed drains. When the bed is empty the suction is broken and the cycle starts again.
2. Continuous flow
A continuous flow bed is the similar to the Ebb and Flow bed except, as the name suggests, the water flows continuously through the gravel to a depth of 250mm leaving the top 50mm of gravel dry
3. Floating Raft.
The floating raft system is what is used by Revalesio at the University of the Nations in Kona, Hawaii (http://foodmachine.org/about/) The grow bed consists of a 300mm deep trough of water with an inlet at one end and an outlet at the other end. Styrofoam rafts float on the water and holes are cut in the rafts to hold hydroponic pots.