I would guess between 1/4 and 1/2 gallon. I let mine get really dry, then water about 1/3 what I think it needs and leave it for a few minutes wile I tend to others. That gives the water time to absorb into the medium. I water 3 times in a ten minute period. I like to see about 1/2 cup come out the bottom into the drip tray. Before I leave the grow I empty all the drain pans. Don't worry about getting the light too close CFL's will only hurt the plant if it touches it for an extended period of time.
Thanks for stopping by my grow!
Peace:smokin: