i flood my system every 6 hrs while lights on...and not at all when its off.if your resevoir is big enuf you need not worry bout it runnin dry..least not within a week or so.the best method for finding how often to water is to let them get a lil thirsty while you time how long it is before they start to wilt...it is totally possible to over water a flood and drain system.your intent is to water them only as often as necessary (which changes depending on plant size,phase,and how deep the roots are into w/ever medium your runnin).

Dive:stoned: