Do fishes sleep? This is a question that has long puzzled scientists and casual observers alike. While it is difficult to say for sure whether or not fishes sleep, there is evidence that suggests that they may indeed do so.
Fishes are unique creatures, and their sleep patterns are not well understood. However, there is some evidence to suggest that they may enter a state of reduced activity at night, similar to what is seen in other animals.
This reduced activity may help them to conserve energy and avoid predators.
While more research is needed to confirm whether or not fishes sleep, the evidence suggests that they may indeed be getting some shut-eye. So the next time you see a fish swimming lazily in a tank, it may just be catching some Zs.
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Toledo Goldfish Standard Fin Koi, Variety of Colors and Patterns - Beautiful Live Fish Perfect for Ponds, Tanks, and Aquariums - 3-4 Inches, 20 Count
$163.00 ($8.15 / Count) (as of 12/10/2025 14:51 GMT +03:00 - More infoProduct prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on [relevant Amazon Site(s), as applicable] at the time of purchase will apply to the purchase of this product.)Toledo Goldfish Butterfly Fin Koi, Variety of Colors and Patterns - Perfect for Ponds or Aquariums - 3-4 Inches, 10 Count
$152.00 ($15.20 / count) (as of 12/10/2025 14:51 GMT +03:00 - More infoProduct prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on [relevant Amazon Site(s), as applicable] at the time of purchase will apply to the purchase of this product.)5 Pack of 3-4 inch Live Butterfly koi Fish
$89.00 (as of 12/10/2025 14:53 GMT +03:00 - More infoProduct prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on [relevant Amazon Site(s), as applicable] at the time of purchase will apply to the purchase of this product.)How many hours does fish sleep?
Fish sleep for about three to four hours a day.
How do you know if fishes are sleeping?
There are several ways to tell if a fish is sleeping. One way is to watch the fish’s behavior.
If the fish is slowly swimming around in a circular or elliptical pattern, it is likely asleep. If the fish is lying on its side with its head down, it is also likely asleep.
Do fishes swim while sleeping?
One potential explanation for why fishes swim while sleeping is that they are using the same muscles to swim and move their bodies around while they are asleep. The muscles that are used to swim are also used to move the fishes around while they are asleep.
Do fish sleep with their eyes open?
Fish do not sleep with their eyes open, they instead close their eyes and rest with their mouths open. This is because when fish sleep they reduce the amount of oxygen they take in and the water expands and presses on their gills.
Summary
It is a common misconception that fish do not sleep. In fact, fish do sleep, but their sleep patterns are very different from ours.
Fish tend to sleep in short bursts throughout the day and night. During these periods of sleep, their metabolism slows down and they become less active.