Deep water culture (DWC) is the one of the oldest method of hydroponics to date. In this system, the plants roots are submerged in water that is aerated typically by using an air pump and air stone. The advantage to this system is the simplicity of technology and high level of humidity in the root zone. The disadvantage of this type of system is that if the source of oxygen in nutrient solution is reduced or fails, there is limited capacity for the plants to maintain vigor. This method is extremely productive and popular for production of lettuce, herbs, and other leafy greens.