Which side should i put the Undertank heater on?

and for people who use timers for their lights, how do you manage to do that if you only use one lamp? or in order to do that do you need to have 2 lamps?

Also, i have very poor sleeping habits, i'm up most of the night, and sleep during the day. He always has the same time between night and day usually, is this bad for him? Like i don't turn on the day light until maybe 4 in the afternoon, and the red lamp at night until like 3 or 4 in the morning. Is this unhealthy?