That's a better question for @Buds Buddy as I flower in 2 gal, or @Emilya Green once she finalizes her set-up. It depends on how big the plant is and what you use to define the reservoir and how much volume that establishes vs what the wicking material takes up.Heyy azi in a 5 gal how much does it take to fill a rez with that 3 or 4 inch space in the bottom ??
Buds is using the commercial version and Em is using drainage pipe. They are probably pretty close in volume though, but I would be curious as well. I think Buds said he was using 20 oz a day for his big girl that threw off more than a pound at harvest.