I check my plants daily. Once morning, once night. I only fill up once a day. They drink at least 1 gallon. It's more like 1 1/2 gallons per day minimum. Hasn't been more than 2 1/2 gallons yet. They did drink around 2 1/2 for a few days though. I have never had a plant this big, my roots take up the entire 5 gallon bucket. I do not wish to do an auto-fill resevoir. Right now money is tight, and if I had money, it'd be going on a 600w setup. With each plant growing 20" high, and 3 feet wide in 1 month 1 week - 1 month 2 weeks, I definitely want a 600!