It's never a wise idea to unplug your filter for anything longer than the time it takes to do a water change. I would say "no" to you planning on leaving it off every night. Can't be healthy for the bb or your fish.
Googled it and found this (from 3 separate reviews):
To turn the light on and off you have reach in on the back of the filter.
The switch for the light is a bit awkward. There is a small switch at the back of the centered contraption and you just pivot it over to the right over the bump and "voila" the light is turned off during the night.
The only improvement I would want is that the LED light switch be moved further to the back of the tank and could be turned off with one easy flick with one finger. The actual switch is behind the filter box and is more like a lever that you need two fingers to move up and down. And you also get your fingers a little wet since the water trickles from the top of the filter box.