i meant what incogneto said, BUT........ I beleive that you could benefit from 30 mins every 4 hrs, or 15 every 2.... but i need to go do some research on drip times with peralite.. Im only using my best judgement on that. So dont make no drastic changes to your timer. Where did you get your info on what to set the timer? And how intense and how close your light is will change that equation.