It would depend on your lights and such, but most likely six is too many. Late in flower one plant can easily drink a gallon a day by itself. It sounds like this unit is made for temporary veg.
I have a choice of lights. CFLs, LEDs, and HPS. The HPS is smaller, just 250 watt, I don't have enough ventilation for it yet, temps are 100F+,
I wont put my plants through that. I know my fatass wouldn't like 103F..... I won't do that to my mj plants.
The unit looks like a knock off of an Emily's Garden hydro system. Same set up, same size parts. It was free, so I can't complain too much. If
it wont work, I can buy other stuff.