Originally Posted by mightymarijuanabuds
if your only going to grow one plant, then the one 125w will be enough, but you may want to hang some mylar ($1.99 emergency blanket from the camping section at wally world, or any outdoors/ backpackers shop) so that the area is smaller... any more plants or a large area would require more light
if the grow area is much larger than the plant then alot of light is wasted, scale it down to just fit the plants you have and more light will be reflected back to the plants
ex: watts per square foot is a pretty good measure for light... you want way more than 50 since this is fluoro (50w per sq.ft. is the rule of thumb for HID lights)... but with just one plant you could hang a divider so that if you have a 4 square foot area now, it becomes half that, basically doubling the light / area ratio, resulting in much more light available for the plant
of course that is the cheap way, and it depends on how many plants you wanna grow.... personally i would use that 125w light in a maximum area of 2 square feet.... my current grow is a micro project that is only 1 square foot for a single plant, running 105w of fluoro light :D