Photoperiods

[Myuu]

Do fish naturally know when it's day and night or do they go by when the lights turn on and off? I am setting up a tank in my bed room, but I'm never in it during the day when I would normally run lights for my other tanks. If I had the tank lights off during the day and on at night would it upset the fish?

 

[fluttermoth]

No, it wouldn't upset the fish. I also have a tank in my bedroom and the lights are on from about 5 or 6 PM until around 1 am and everything is fine