Hey Marine,
I wouldn't turn off your power heads at night because they help export waste. You would have some settling at night, and that would lead to a build-up of nutrients over time.
If you have a controllable wave-maker/pump combo, dialing back the power of the power heads would be OK, as like a night mode, gentler current at night.
My wavemaker and pumps are not controllable, but what I like to do is decrease the frequency of the wavemaker at night. Where they might alternate every 15-25 seconds during the day, I increase the time at night to make them alternate every 35-45 seconds at night. This doesn't decrease the power of the power head, but I still think it gives everybody a different feel at night.
I also mix up the wave frequency all the time, not just the examples above. I think variation of the wave frequency gives it a more natural feel. I always try to vary it a little every day. Keeps everybody on their toes!! Unfortunately without a controller, I have to do this manually, but it's just a little twist of a knob.