SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/fish-lights-not-all-day

Is it OK to leave aquarium lights on 24 hours a day?

No. Fish need a day and night cycle.

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  1. Yes, fish like constant light
  2. Only for goldfish
  3. No, fish need a day and night cycle ✔

Why: Merck says lights on 24 hours a day, 7 days a week stress fish and leave them more likely to get sick. Purdue adds that constant light may cause algae problems.

Huh, didn't know that: A Texas A&M goldfish guide says not to leave the tank light on more than 12 hours a day.

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What kind of fish goes best with ice cream? A jellyfish.
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References

Answer: No, fish need a day and night cycle. Merck says lights on 24 hours a day, 7 days a week stress fish and leave them more likely to get sick. Purdue adds that constant light may cause algae problems.

  1. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    Leaving the lights on 24 hours a day, 7 days a week stresses fish
    Checked 2026-10-11.
  2. Texas A&M AgriLife Extension: Gold Rush, A Kid's Guide to Goldfish Care extension.rwfm.tamu.edu/wp-content/uploads/sites/8/2013/10/Goldrush-%E2%80%93-A-Kid%E2%80%99s-guide-To-Goldfish-Care.pdf
    Do not leave the light on more than 12 hours a day.
    Checked 2026-10-11.

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