I probibly should have clarified.. i meant 5gal/plant is perfect but you can def get away with a lot les.. shit u can do 1gal/plant. when it comes to hydro, i dont believe there is a specific rule of thumb for the res volume.I dissagree but agree entirely. U can grow more plants per square foot by introducing different grow styles into each system. Im growing 13 plants in a single 18 gallon res using Al b fucts system and ideas.
U can mainupulate these plants to pertain entirely to ur needs.
Ive harvested 3 plants in a 5 gallon bucket with no problems.
It all depends on grow experience knowing what to expect and being able to control the environment ur plants r growing in.