This is what I did for a 4×4. ten cxb3590 3500k , 2 HLG -240-1400ma. that is a 4×4 in the pic and it's almost the same size. now you don't have to go that far but if you want the most out of your grow this is what I recommend. but you can go as low as 6 cobbs and that will work to ,but I...