i surround my plants with candles and pray to the four winds dressed as a druid.....nah mate hps if u can only afford one, most new ones are dual spectrum so they have sum of the blue spectrum thats best for vegging as well as the red spectrum for flowering, if u can afford two then like the guys above say mh=veg(nice tight node spacing)-hps=flower(high lumens for more bud growth). fluros/cfl can be used and they are cheaper but slower and with less growth rate, although i use them for my clones/seedlings and mother plant coz there very gentle on new growth and dont require heat venting.