I never used jacks for hydro,just peat based and coco grows. I would guess you would need more than 1 of the 4# tubs to do a full run in a 40 gal system at full speed.but not alot more than 1 maybe 1.5 tubs to finish.i use half as much as hydro guys running just 600ppm or 1.2 ec sometimes i was only using like 300ppm or .6ish ec :)
I would say finish the run your on with your current nutes
yeah, I was definitely going to finish this run with what I'm doing. I was just looking to see if there was something better. I just bought GH flora 1 gallon 3 part set for $80. That's good for 4 cycles for me. I'm not unhappy with GH except they are owned my Scotts who is owned by "the company that shall not be mentioned" (Monsanto).