Current set up is looking like 5+ plants growing in a fairly tall and narrow closet space (Not a walk in closet, in other words) under 400w HPS. I remember reading some excellent info about the use of co2 in a grow on overgrow, but I've since...forgotten it. Does the co2 need to be present during light's on or off? I'm a little worried about the temperature in the grow space since I will probably have to seal the space to get the ppm up to a noticable level. I still remember plenty about how useful it is during veg, is it as useful during flowering? Im probably going to end up using dry ice, but does anyone know any good alternatives aside from a propane powered co2 generator? I'm also wondering about light reflection, since I don't want to neglect all the bottom leaves, If I remember correctly white paint (Any information about what kind of white paint would be much appreciated) reflects about 75% of the light that hits it, while others can go up to 95% (Too expensive for my budget). So if anyone could shed some light on the white paint that would be great.