I am goin to use 3 400 watt radiums and have just traded my dula 250 watt for another 400 watt. I may run the 2 additional bulbs with 65K bulbs in between the 20K for 3 hours a day and see what happens. It would be 2000 watts on a 180 for 3 hours a day and 1200 for 7 hours. Because the corals seem to respond bettre in coloration IMO I am definatly using the 3-20K bulbs.