THE FLOATING BED SYSTEM
The simplest of all of the active systems is the floating bed
In it, the plants are anchoured in a floating platform placed directly on the surface of the nutrient solution contained in a container while the roots remain completly or partially submerged in this solution.
It is necessary to oxygenate the solution by bubbling air through an air pump, a blower or even by recirculating the solution periodically.
When oxygenating the solution by bubbling air through it, this system is considered a passive one.
However, as mentioned previously, oxygenation can be accomplished by recirculating the solution by means of a pump, sometimes using an air injector, in which case, this system is considered na active one.
This system is generally used for small plants that need very large quantities of water, as is the case of lettuce, which produces enormous productivity yelds when cultivated in the floating bed system.
It is also ideal for demonstrative purposes in schoolrooms where it can be mounted using fish aquariuns.
The biggest limitation is its inadequacy for medium and large sized plants that have long life cycles.
When cultivating larger plants it is common to attach the platform over the sides of the solution container, in which case it becomes known as the Fixed Bed System or Gerike's System.
It is very commonly used with medium sized plants, such as tomatoes, where an auxiliary structure is added in order to guide and support the tomato plants.
Today, it is more commonly used in external domestic orchards, in plant nutrition research labs and for school demonstrations.