Light acclimation

[Myka]

Going from 150w to 400w is a big increase watch your corals VERY carefully. If you notice any bleaching or poor reaction give them a day of actinics only (or darkness if no actinics). What was the Kelvin of the 150w? Did you change reflectors too? What about ballast?

Do you have actinics that will remain on during the entire photoperiod? If not, I'd say turn the MH on at the usual time in the morning increasing the length by 30 minutes every 2-3 days. If yes, then turn the MH on in the middle of the usual photoperiod increasing 30 minutes alternating from adding it to the beginning and adding it to the end every 2-3 days.