Your not thinking properly my friend. First, you cant use the lid that comes with the 100 gallon res, to flimsy and collapses when plant gets to heavy. You have to use a lid mde out of plywood covered in plastic with the hole for your net pot. ok, you lose some net pot height right there. The 100 gallon res is 4ft x 4ft and 12 inches tall. I am not sure typing this what the height of a net pot is but lets say 8 inches, so we have res, 12 inches and plywood 1/2 inch gives us a total of 12.5 inches minus 8 inches for net pot. that leaves 4.5 inches plus an inch of water in the bottom of the net pot for a TOTAL of 5.5 inches of nutes in your 100 gallon res.... so approx 45 gallons of water total per 100 gallon res for each plant. Dude, 8 - 3 lb plants per 24 hour period use 75 gallons of water at week 4 of flower when humidity is at a steady 40%.
Huge lesson here guys, you have to have a main res that you can fill on fri and only have to top up small amounts of water and nutes before you change out the system the following fri.
hope this helps mate
dds