The floating raft method (a variation of the deep-water culture method) and the flood-and-drain method (also known as ebb-and-flow method) are two very popular hydroponic growing methods. Each method is better-suited to certain types of plants, and each method has its advantages and drawbacks. Either method, however, can be counted on to produce lush, productive plants when implemented correctly.
Modern hydroponics gained widespread fame beginning in the late 1930s, due mainly to the work of professor William F. Gericke of the University of California at Berkeley and his 1940 book, "Complete Guide to Soilless Gardening."
For deep water culture, the plant is placed in a "net pot." A bucket or other container with a lid is used to contain the nutrient water. The net pot is suspended over the nutrient solution surface by placing it partway through a hole cut in the lid of the bucket; thus, only the roots of the plant are partially submerged. The nutrient water is aerated using an aquarium-style air pump and air stone. The oxygenated water facilitates greater oxygen and nutrient uptake by the plant roots. The floating raft method simply substitutes a floating Styrofoam "raft" for the bucket lid.
For the flood-and-drain method, the plants are suspended in a separate, usually tubular, grow chamber made of PVC pipe mounted horizontally. A timed water pump or float valve allows nutrient water to flood the grow chamber to a predetermined level. After a timed interval, the water is allowed to drain back into the separate nutrient reservoir. After another interval, the cycle repeats.
The floating raft method was a revolution for plants such as lettuce that require continuous access to large quantities of both water and nutrients, as their roots are continuously submerged. For the same reason, it allows a closer spacing between plants, maximizing space efficiency in commercial facilities.
The flood-and-drain method allowed scientifically minded growers and researchers the means to deliver a more precise, optimized feeding program for specific crops and ornamentals.
Its simple design and function make the floating raft method an ideal choice for the home hydroponics enthusiast. There are no drip or spray emitters to clog or timers to fail. The lack of emitters make it a good method to use if you want to give organic hydroponic growing systems a try. Power outages of no more than a few hours are easily withstood without permanent damage to the plants.
With the flood-and-drain method, the parts and operation of this growing system are also fairly simplified, so it's a good choice for do-it-yourselfers. If you have a high-quality water pump that can stand up to a little abuse from the occasional granule of nutrient or piece of root material, then this method is great for trying organic hydroponics. Install a particulate filter upstream of the pump for the most dependable operation.
Both methods are not amenable to power outages lasting more than a few hours. Have a backup power source available, such as an emergency generator or the judicious application of an uninterruptible power supply. This is true of all methods of hydroponic agriculture, and its single largest disadvantage.