moonlights don't do anything for the inhabitants. they are just for your own enjoyment. consider them if you like to barely see into the tank when they lights are off.
the dawn/dusk simulation is also for your enjoyment, as it does nothing for corals or fish. the actinics and daylights are still turned on immediately on your t-5 fixture, so the fish will be just as startled.
as for a time frame, i would suggest to try and mimic the natural day out at the reefs where your corals are collected.