Lights On?

Nope. If you don't have any plants, lighting other than normal room lighting is pretty well just for your viewing. As long as the tank is exposed to 'normal' lighting cycles, ie, a period of day, followed by a period of night, the fish will be fine.
 
Depending on your light setup you may wish to put your lights on a timer so they come on an go off the same time each day.
 
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