there is a way to tell how much bubbles u need. u multiply however many gallons your system is by 28 and thats how many liters of bubbles u need. u can multiply it by 15 to and wont c much of a diff in performance
u cant tell how much it will yeild it depends on how u grow if really work at it u can yeild 4 oz a plant. ive hear that the longer the roots are the more u will yeild.