Hydroponic systems use highly oxygenated water with liquid fertilizers to grow plants. Hydroponics or soilless gardening techniques have no soil for the plant to hold on to. Hydroponics can also be used for plant propagation. Deep water culture uses a water bath with a bubbling air stone at the bottom. ZEN PRODUCTS has a four site window sill hydroponic system. Perfect for table lettuce, greens and smaller vegetative plants. It holds approximately one gallon of nutrient rich water.