Do Fish Ever Sleep? Here Are The Signs To Look For

You can easily tell when your dog or cat has drifted off — they close their eyes, get lost in dreams, and sometimes even snore, just like humans do. But your pet fish is a different story. That little guy or gal lives in the water and, as Dory would say, "just keeps swimming," seemingly all day and all night. Does your goldfish ever sleep? The answer is nuanced.

Yes, fish sleep. Kind of. They may enter periods of lower activity and metabolism function, but they probably won't look like they're asleep. In fact, they often appear more alert than other animals while resting, potentially so they can react to threats. However, according to a 2019 study published in Nature, zebrafish have at least two stages of sleep that resemble those found in our own sleep cycle. (Humans move through four stages of sleep total.)

Significantly, researchers have observed fish settling in for a snooze at night, meaning your pet fish may be on a similar sleep schedule to you. Philippe Mourrain, PhD, an associate professor of psychiatry and behavioral sciences at Stanford University, said "the only real difference is a lack of rapid eye movement" when it comes to zebrafish sleep vs. human sleep (per Stanford Medicine).

Since fish sleep looks different than human sleep, how can you tell when your little buddy has powered down? Well, some fish find a hidden spot in mud or coral to tuck themselves away while they rest. In your aquarium, they might burrow inside a log or under a grotto. Given this, it's always a good idea to provide structures and toys for your aquarium fish. Other fish will just float in one spot for a while. Generally, they may be less responsive during periods of rest.

Some fish are diurnal, meaning they sleep at night, while others are nocturnal and do most of their swimming and searching for food after sundown. Zebrafish researchers discovered that exposure to light interrupted their sleep, suggesting they may have a circadian rhythm, the cycle that describes why some animals, including humans, feel awake and alert during the day and get tired at night. So believe it or not, there may be some steps you can take to foster healthy sleep patterns for your pet fish.

The majority of aquarium fish are diurnal, so they'll operate on a similar schedule to you. Since it was found that light exposure can cause sleep deprivation in zebrafish, the simplest way to help your buddy maintain healthy sleep habits is to get an aquarium light with a timer, one that has set hours of operation. Different fish have different needs when it comes to the ideal number of hours of light exposure, so make sure you do your research and place the aquarium in a spot in your home that gets the right amount of light.

If possible, it's probably best not to throw a rager complete with pulsing music and flashing lights while your fish is resting. And if you notice your little bud lying at the bottom of your aquarium, floating in one place, don't go tapping on the glass to wake them up. You wouldn't like if someone did that to you, and clearly, fish have more in common with us than we may have thought, especially when it comes to sleep.