for size of box im thinking 6 but i would say go with 4 u can still get great yelled and do a veg box keep some in there tell rdy to move them over that way u can cut time out so u be geting 6 plaints ever 8-12 weeks
u could just get a pump and do top drip 20 dollars done and u wont run out of water i used the aquaglobes with my reg plaints and they will go thou one in a day if its hot pick up a pump and 20gal box from walmart and some hose and done all for around 20 bucks