Is it bad if I accidentally leave the lights lit on a fish tank overnight? Or do the fish not care whether it is light or dark?

  • I'm curious myself... – John Cavan Oct 9 '13 at 15:30
  • @JohnCavan I've actually wondered about this for a while :P – Timtech Oct 9 '13 at 15:31

Fish do care if it´s day or night: they have a cicardian rhythm and many physiological events are related to the day / night time. Light could interfere with that. Source: this book, chapter 6.

Even blind fish can have a cicardian rhythm

Leaving the aquarium light accidentally lit for one night won´t instantly kill them but will cause some stress.

  • Why not just connect your lights to a timer that will shut it off automatically at a given time each day?! – martin Oct 9 '13 at 18:56
  • 1
    Also leaving the lights on for long periods can increase algae growth - which, as well as being unsightly, can decrease oxygen levels in the tank. – starsplusplus Jul 18 '14 at 12:41
  • 1
    As an addendum, the night is also required for some plants. Compare for example this question. – Voitcus Jun 2 '15 at 10:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.