There’s no one perfect method, most seem to recommend a reverse photoperiod to the main display for two reasons:
1) PH control
2) dark period for photosynthesis
having a reverse photoperiod (refugium lit overnight and “dark” during the day) allows for photosynthesis to occur 24 hours a day(12 when your display tank lights are on and 12 when your refugium is on). Ph will actually increase while the lights are on and then lower when they are off. Using a reverse photoperiod for refugiums seems to stabilize the ph swings.
most plants have been found to grow better whe