hydroponics is quite simple really. generally u have a resivoir below the level of ur table (or buckets).. being lower allows water to drain down since it cant go up..
u generally have a pump that pumps water into ur table or buckets, and a drain (generally a tube that sticks a couple inches above the bottom of ur try to allow water to fill a little ways)...
water will go down this tube (pump continueing to pump water) when the water level reaches that high (basically is a levy, allowing water to get 3inches deep, then running over flow down tube).. the pump shuts off (on a timer) and water will drain back down the pump and its tube to ur resivoir..
its all pretty simple.. just remember that water will drain back through ur submersiable pump.
"An ounce of prevention equals a pound of cure."
treat it before u get it