Take control of your hydroponic system with this General Hydroponics GH4520 controller system today! This controller is a very simple and easy to use device - a container with a float valve that connects to the line of units. A reservoir filled with water and nutrients is located on top of the float valve and is operated by the controller. This system can accommodate up to 12 Farm modules maximum. System includes a 13-gallon reservoir with grommet fittings, blue 1/2-inch tubing, 8-gallon controller with float valve, seven (7) 1/2-inch barbed tees, and two (2) 1/2-inch elbows.