yeah i got ventilation i have an inline fan sucking air out the top through a carbon filter and an inline fan blowin cool air into the bottom.that pic is when i was building the box.also i have 2 250w lights at the moment if i get a 400w would that be less light?cheers for the help +rep..how close can you get a 400w hps with cooltube and ventilation?Yes, 600w would be too hot even if you were venting it well. I'd go 400w at most, maybe even 250w. As far as distance of light over plants, get it as close to the plants as possible without burning them. Do the hand test. If it's too hot for your hand, it's too hot for your plants. Do you have any air flow/ventilation in that box?