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FAQ - Do fish sleep when the lights are off?


Question: FAQ - Do fish sleep when the lights are off?
I usually leave my light on over night and I leave it off during the day. When I get home from work and turn my light on, my three damsels seem to be very drowsy. One damsel sits on the the bottom of the tank. It almost seems like he is about ready to die. Is this normal? Are these fish sleeping when the light is off? After a few minutes, the fish seem normal again. How long should I be keeping my lights on?
Answer: Just like any living creature on this earth, fish sleep too. Most of the time if they are not hiding in a hole or house, they'll prop themselves up against something. When a tank is dark and you shine a flashlight on the fish, they act dazed and swim around confused for a few minutes. The same thing happens when you dive the reef at night. Fish that are not nocturnal are tucked away in their houses, fast asleep. It is normal. As far as how long you should leave the lights on, it sounds like you have a pretty good schedule set up on a regular basis for your fish already.

For more information about saltwater animals and their habits, refer to our Fish & Invertebrate Care Resources, and to learn more about lighting an aquarium, refer to go our Lighting Resources.

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