Distancia de la lampara

I use the 450w mars light in my 150x150x200. I have to hang the light at the very top towards the end. I'd start the light 3 feet (36 inches) above any seedling run on 50% for the first week. That light is very powerful, maybe too powerful for that sized tent. You will be fine, just keep a close eye on them. Raise the light as the plants grow, and use training, topping, lst or anything that will keep the height of the plants equal.