Ultimately, nobody can tell you how close to put the lights, that entirely depends on the design of your reflector. When the plants start to burn, raise the lights. Try to have the lights at least as far away from the plants as the height of the plants. With an open shelf, try to arrange the plants so that they are all the same distance from the lights. Or surround at least three sides with white sheeting and then it won't matter.
from
http://cactiguide.com/article/...
about the bulbs...
try giving the people at Greners.com a call. Kinda wrong plants but i bet they would be able to help regardless.
good luck
