There are a lot of things we’re still learning about the animal kingdom. We’ve heard myths all our lives and formed many of our own beliefs and expectations on those things we “learned” as kids.
One of those things is that fish don’t sleep. I mean, when you look in a fish tank, they don’t look like they’re sleeping, right? So it must be true. But is it really?
Let’s take a look at some of the things researchers and experts have learned over the years, watching these fascinating creatures.
So, Do Fish Sleep?
Almost every animal sleeps. Living on land or in the water makes no difference. There is a common myth that aquarium (or paludarium) fish do not sleep, this is because not every fish looks the same when they sleep. People are used to seeing land animals lay down and close their when they sleep but fish don’t follow this pattern, even when they’re in their REM cycle.
Most fish must have some sort of momentum while they sleep to have oxygen. Except for sharks, fish do not close their eyes because nearly all fish lack eyelids. The one thing fish have in common with all animals’ circadian rhythms is that when they sleep, their metabolism slows down, they can rest and heal.
How Do You Tell When Fish Are Sleeping?
The easiest way to know if your fish are sleeping is to observe their behavior. Fish keep routines like other animals and certain species like to be either at the bottom of the tank or near the surface of the water. Depending on the species of fish, they may want to sleep around rocks or other items on the bottom of your tank. Others choose to sleep in the middle of the water and will not even wake if you pick them up.
During their time of sleep, they will be less responsive to any stimulus or may just ignore everything around them. One of the easiest ways to tell if they are is asleep is to watch their gills, when fish sleep the gills will move slower than normal.
Where Do Fish Sleep?
Every species of fish has a different location in the tank where it prefers to sleep. When certain species of fish fall asleep, they will float along motionlessly on the surface of the tank. Other fish love to be on the bottom of the tank, while some fish go as far as to bury themselves under the sand.
Fish have sleep patterns just like humans do. If you are new to fishkeeping, the lack of motion while fish sleep may scare you into thinking they are hurt or dead. Most likely, they’re just sleeping unless other tell-tale signs appear.
Some species of fish make their own kind of sleeping bag or cocoon out of mucus. One of these fish is the parrotfish. Goldfish prefer to sleep near aquarium decorations. Betta fish generally nestle into the gravel at the bottom of the fish tank.
How Do Fish Know When to Sleep?
Fish are like most animals and have an internal clock that lets them know when it is time to eat or sleep. While turning off the lights at nighttime will help your fish sleep, they will still get shuteye even if lights are accidentally left on.
Different species of fish will sleep at different times. Some fish are diurnal, which means that they will sleep at night and move around during the day. Other fish are nocturnal and will sleep during the day and move around at night. It’s vital to make sure you have fish that are not aggressive during the sleep period of other fish, or your fish will not be able to get the sleep they need and may become sick.
Something to keep in mind is if you are breeding fish, certain fish will not sleep while they are raising their young. Also, certain breeds of fish will not sleep at all until they are around five to six months old.
Another thing to keep in mind is that certain fish will not sleep when they migrate. While fish are not able to migrate while living in a tank, certain breeds will not sleep for a period while moving tanks.
Don’t Some Fish Have to Keep Swimming All the Time?
Even in fish who live in the dark and never see light, studies have shown that the fish have low brain activity that resembles sleep.
Certain species of fish, like sharks or tuna, always must remain swimming to keep breathing. They accomplish this feat because their brain still operates and makes them move while sleeping.
Do Fish Dream While They Sleep?
Do fish have dreams and nightmares? This is a question scientists have not been able to discover a conclusive answer to.
An unrelated species, but a fellow water dweller might have answers. There are video recordings of a sleeping octopus vividly changing the color and patterns on its skin. It’s normal for an octopus to only change their colors when they are hunting or evading predators, so all the changes occurring during sleep make scientists think that the octopus was having vivid dreams.
How Long Do Fish Need to Sleep?
Fish have varying sleep needs. Not every fish species needs the same number of hours of sleep. Furthermore, environmental factors and how active the fish are helps to determine how much sleep your fish needs to be healthy and happy.
Sleeping habits among fish species vary. Some fish take naps and other sleep only one time during the day or night. However, studies have shown that fish are known to adjust their sleep schedule to the fish tank they live in. Turning the lights off when you go to bed will help encourage your fish to follow your sleep schedule, that way you can see them during the day when they most active.
Can Fish Have Sleeping Issues Or Disorders?
Even while sleep, fish are still able to be on the outlook for danger. Fear of predators is not the only reason a fish may not sleep well. There are events in a fish life that can disrupt the normal fish sleep cycle. Migrating, spawning, and raising babies may cause fish to lose out on normal sleep at the same time.
Is There Anything You Can Do to Make Sure Your Fish Sleeps Enough?
If you want an easy way to make sure that your fish will get enough sleep, use a timer with your aquarium.
Timers help your fish to develop a regular day and night cycle. If you provide places for your fish to duck and hide in, this will give them areas they can feel safe while they rest.