I've been reading all that I could before I purchase my equipment and I have a question on the lights. I'm seeing lights that say great for flowering and great for veg stage, so do I need 2 different lights. I was planning on buying a 400 hps light for my closet grow. Will this single light work for my whole grow? Thanks, BarleyMob
You could flower and veg with a 400 watt HPS, but it wouldn't be as efficient as if you had 400 watts in 6500k or 5000k color spectrum during veg. Also, a lot of the time you can get a MH/HPS combo grow light for maybe 50 dollars more, if you only have one room. It will work and it will probably do a good job, but if you have the money to get another it would be better.
You could get a switchable ballast or a MH conversion bulb to use during veg. That said, you don't HAVE to use two different spectrums, but MH are the best at keeping plants compact which is what you're looking for during veg. HPS will give you bigger yields than MH during flowering.
As the others said, it's better to do MH for veg and HPS for flower, but HPS will work for veg as well. If you do want to do 2 lights you should plan your setup so you only need two different bulbs, not two different lamps. The hood and socket are the same for either HPS or MH, it's the ballast you have to take notice of -- a digital ballast can accept either type of bulb, a switchable ballast can as well (but you have to flip a switch), or if you have just a HPS ballast you can get a MH conversion bulb, which is designed to work off a HPS ballast.