Jim, there's been a few threads dealing with this topic - search for 'photoperiod' or whatnot. (Here, try this:
http://www.canreef.com/phpBB2/viewto...ht=photoperiod). Look for Steve's post on p 2.
The best method agreed on seems to be the multiple timer settings for the halides, where you start with a portion of each hour (15-20 mins), and ramp up to the full 60 minutes over a period of days or weeks.
HTH