when i first ran mine i ran them for 1 hour a day for a week, than 2 hours a day for a week and so on. i had corals that i did'nt want to burn. everything worked out fine. i leave my 1- 20k 400w on for 8 hours and my 2- 10k 250w on for 6 hours. are you going to do sps? what size tank?