this is prolly best for an all indica grow with 4...but you can do 6...as you can see I only use 4. The roots haven't probably filled the res up halfway...holds approx 10 gallons max...but 7 recommended. I only use 2-3 gallons for all 4. I use a bit above half nute strength and top up with plain water every 4 days, and change the res completely every week or every week and few days. I like to add a bit lower concetration, because in a few days, the water level goes down and the concentration rises. I wouldn't recommend an all sativa grow though unless you LST/Jog them. But since I keep them all under 2 foot tall, I have no problems. I also didn't start using my pump this second round at all until today. I've had no problems, and I've actually seen better growth, but recently, since I have soo much of roots in the res, I needed a boost of aeration. I keep the drip time on 24/7...no root rot soo far. I don't use any temp guages other than my hand for distance from plants, and temp of res. I'm only growing as much as I need for myself and for an MS patient..and not much is needed, so thats why there are soo few. My main experience is with outdoor soil, with little to no maintenance. So, hydro is something to look forward to for me..I've seen nothing but fantastic results soo far, and I know all there is to know on the subject. I would never go back to soil myself. But I would like to grow hydro outside. And also, I'm using only 3 inch netpots..and look at my 1 month results, andI'm using approx. less than 1 gallon of PH'd tap water per plant...so you can do it with less, and not a whole lot of maintenance.