Each Grow Flow Controller Unit can control up to 24 of our 5-gallon growing modules, and up to 48 2-gallon modules. Includes one 7-gallon controller bucket, premium Grasslin timer, two 250 GPH pumps, all fittings, half-inch tubing for pumps, and sample nutrients.Active Aqua's Grow Flow is the most efficient ebb & flow system on the market. With the Grow Flow's easy-to-program controller unit, you can pretty much "set it and forget it." And since your pumps are only pumping a short time each day, the system is extremely reliable and efficient. Just set the fill and drain cycles, and the controller unit does the rest! As for safety, the Grow Flow is the only unit available with fail-safe overflow protection. If the float valve stops operating, the LED indicator lights up on the control panel and the emergency shut-off valve automatically shuts down the system, preventing any spillage or damage to your growing area. Have bigger plans? With our convenient Grow Flow Expansion Kits (sold separately) you can connect up to 24 growing modules to a single 5-gallon system and up to 48 modules with the 2-gallon system! You can also build your own system from the ground up by purchasing all the components individually.