3-4 full size plants tops under a 400. Put it as close as you can without burning. All depends on the bulb and reflector type. Some bulbs are a little more effecient and throw of different amounts of heat. In my Air cooled reflector I could get my 400 about 12 inches form the plant tops safely
thanks for the advice i hope i get good enoug to grow some of that ww i am scared to buy seeds on internet btw can you recomend a good fert that i can get a local wally world or home depot
hard to say.. each locality sells slightly different stuff. Stay away from MG all together. Wy dont you go shopping around see what they got, make a list and come back here and tell us what you have available.
Note Brand, mix, and the N-P-K values. Have you looked to see if you have any hydro shops you can visit locally? They have the best stuff. Its especially good for beginners since it is very easy to use, and I swear most of it was made for cannabis.