TURBOGARDEN ™ features a 25 gallon reservoir, which contains a mineral rich nutrient solution. Periodically, the nutrient solution is pumped up to the top grow tray to water and nourish the plants until the grow media and roots are adequately hydrated. The timer will then shut off the pump, the solution drains back to the reservoir, and the process starts all over again in a few minutes or a few hours later. To maintain the 22"x36" hydrogarden, simply top off water, add nutrients at one quarter strength, adjust pH to 6.0 and change reservoir every few weeks.