On the 12hr schedule I feed 6 times for 15 mins each feeding. First feeding when the lights come on and last feeding 15 mins before lights shut off. The room in the picture is about 4x4x84 and my other room is an old sauna room at 4x5x84. The smaller room will be my starter room and the sauna's going to be dismantled to make room for a new room that will be about 4x10x84. I'm running 1000 watt Hortilux super hps in each room. They're both air cooled and both rooms have a charcoal filter for the smell and co2 bags hanging. I'm retired now and have plenty of time to make sure the ppm and ph are right where they should be. I check all totes twice a day if possible. I find that every time I check I have to add water due to evaporation and feeding. The ppm level increases by 100 points or so in just 8 hrs. If you don't check your ppm often you'll end up burning your plant; keep the ppm level on the low side of the scale. I use General Hydroponics nutrients and go by this chart.
Maybe now that I've covered the sides I won't have to change the nutrients as often.