20/4 or 24 hrs a day. I do the 20/4 for veg personally. I'll veg them for anywhere from 45 to 60 days and then flip them to 12/12. A lot of people swear by having the lights on 24 hrs for veg, and that works well and has for years, but I personally feel the plants NEED the 4 hrs of dark. I doubt they need more tho...