Sorry i don't know how much 12" is....in Europe we use the metric system....
You should use the hand test... put your hand under the lamp ,and the distance where it wont burn your hand ,(plus a few ( " ) ), the plants are safe...
The closer they are , the more light they get,the faster they will grow...

That weasel is btw. very cute...
zebulon Reviewed by zebulon on . 2nd grow My plan : - germinating using paper towel method, then planting poped beans in party cups to srpout. - 4 parts Fox Farm Ocean Forrest to 1 part pearlite for my potting mix. - ill be using blue standard incandecents to gro sprout to an inch or 2, then transplanting to my 1 gal pots. - Plan on using 1 gal. pots for veg, and 3 gal. for flowering? advice on those sizes would be good? - 1 400w MH conv. HPS for veg and flower respectively. - 1 bag seed (already popped and under incandecant) Rating: 5