actually, "in nature" corals do not receive 9 hours of intense light. Due to refraction (the way water reflects and distorts light), the amount of intense light is only about 4-6 hours in the wild. It is amazing the amount of difference between the amount of light penetration at 10am and at noon because the water surface reflects more at non-90 degree angles. That small of angle really changes the intensity. Because our lighting system in our tank are less intense normally than natural sunlight, it is "ok" to run longer photoperiods. That being said, what is natural is more of a gradual increase/decrease with only a limited amount of full strength lighting. As a result, corals tend to do all then need to do photosynthetically in about a 4-6 hour range.