https://www.chewy.com/education/fish/general/do-fish-sleep
While fish do sleep, it is not quite the same as the deep, restful slumber we experience when we close our eyes.
Rather than a full, deep sleep, fish enter a "low power mode." They still need to remain aware of their surroundings, so their sleep is lighter. Unlike mammals, fish do not have eyelids, meaning their eyes stay open while they sleep. When they do rest, they slow down, hovering in a comfortable spot with slightly reduced alertness. This allows them to take a break while still being able to react quickly to sudden movements or threats.
During sleep, fish lower their metabolic rate, breathing, and movement, helping them conserve energy and recover from physical exertion - much like humans and other animals.
Most fish in a standard aquarium will likely sleep when it gets dark, which is why it is important to give them periods of darkness each day. This helps ensure they get restful sleep and aren’t kept under bright lights around the clock.
As for how long fish sleep, it varies by species, but many fish rest for several hours each day, typically during low light or dark periods. While fish do not actively swim while sleeping, you may notice slight movements. They often find a cozy spot to hover, sometimes bracing themselves against rocks or ornaments to avoid being pushed around by water currents.
The next time you observe your fish, you will have a deeper understanding of their sleep behaviors, thanks to the insights from the Chewy editorial team.
