Do fish sleep? Great question right? Fish have no eyelids and can’t shut their eyes. Also fish have no cortex within the brain that usually allows us to dream.
When we observe other animals and humans, we tend to see slower breathing, twitching of muscles, and movement of limbs. So we don’t see this in our fish the question is do fish sleep? Can we tell if the fish are sleeping?
Do Fish Sleep
Yes, fish sleep most will sleep at night we can observe lower gill mouth movent and less breathing a reduced metabolic rate, and a slow brain wave pattern.
So fish sleep how do we know about brain wave patterns? What about deep sleep don’t you need rapid eye movement check out this article fish sleep like us for more on paradoxical sleep.
Suffice it to say there has been much research on this topic. It now appears fish sleep in all manner of ways similar to us so keep reading.
Can We Tell If A Fish Is Sleeping
Yes as most fish will find a place to sleep either between rocks or shrubs or even bury themselves under the substrate. Some fish will just rest near the bottom but they will be motionless.
Fun fact some fish can make a kind of slime cocoon that they use to sleep in much like a sleeping bed.
How do we really know they are asleep? I mean some people will argue the true definition of sleeping is ” The resting of the body and the mind by closing your eyes and becoming unconscious”.
This is only one reading and there are plenty of others that don’t mention the shutting of eyes
here’s one from the Cambridge dictionary “the resting state in which the body is not active and the mind is unconscious:” As we can see no mention of eyes or neocortex both of which are sometimes used to define sleep or dreaming. Although we know fish have neither.
For some extra weight to my argument have you ever seen someone sleeping with their eyes open yep I have too, in fact, I’ve occasionally slept with my eyes open. Was I not asleep I don’t remember anything.
How Do Fish Sleep
Fish slow down all vital functions allowing them to take in less oxygen they breathe slower move less and rest they alternate between shutting down one side of the brain to save more energy while sleeping.
Fish like us are diurnal meaning they move around in the daytime and rest at night. Once we turn the lights off their brain slows down. Metabolism slows too as we observe them they will start looking for their bed it doesn’t take long.
Why Do Fish Sleep
Similar to us fish when sleeping can heal themselves build their strength up replenish nutrients even regrow tissue. Of course, sleeping helps with the nervous system and the immune system. While asleep fish can fight off bugs parasites and diseases. We need to keep an eye on them and give them a helping hand along the way of course.
Sometimes fish can sleep as a defense mechanism here’s an article on neon tetras playing dead yep these fish are known to play dead or sleep to avoid certain predators. Although in general fish sleep to recharge much in the same way we do.
When Fish Sleep
As stated earlier fish tend to sleep at night the same as us. But there are those exceptions Plecos and knife fish are two obvious nocturnal fish. These will be up at night and sleeping during the day usually hidden inside a cave or an ornament.
With this in mind, we should always make sure what tankmates we are going to keep together as one will affect the other.
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Do Fish Suffer From Lack Of Sleep
Again yes studies over the years have detected sleep deprivation causing behavior issues. It looks like fish get tetchy when tiered the same as us. Fish have also been observed with insomnia check this paper out for more details.
Zebrafish have been extensively studied. It’s believed they do indeed suffer from sleep deprivation but they will catch up on said sleep the first chance they get remind you of anyone. Electrical shocks and light were used to keep the fish awake. After they were left alone they made sure to catch up with some beauty sleep.
So some fish sleep at night and some sleep by day and fish do need beauty sleep to recharge and heal. Is this the case for all fish?
Do All Fish Sleep
There are some exceptions to sleep. Nap may be a better term some giant schooling fish need constant water flow over their gills. So the fish in the middle of the pack may take a nap while the rest keep watch and then change turns.
Also the shark now the shark needs to be perpetually moving forwards in order to get enough oxygen over their gills so they do sleep but they are still moving strangely.
Another cool fact is the cave fish now they are constantly in the dark and pretty much blind too. It’s believed they do slow down but probably don’t sleep much.
How Do I Know My Fish Is Sleeping
If they have disappeared into a corner of the tank or bottom and haven’t moved for a few minutes. If a little tap on the glass gets no reaction or a bit of food has no effect. Chances are your fish is sleeping.
Or your fish has gone between some nice coral or other rock or maybe some nice shrubbery yep he’s after some shut-eye. Of course, if he’s gone inside a cave tunnel or ornament he’s sleeping.
Last but not least some fish just love to have a kip under the substrate they will burry themselves nicely tucked up and off to sleep.
Improving Fish Sleep
How we can actively improve our fish sleep. First, make sure there are plenty of hiding places in the tank. Make sure there are good rocks shrubs plants to hide in. A tunnel or cave-like structure does well for a lot of fish.
Wood can be good a deep enough substrate for those that like digging. Having the top of the water at the surface covered with some leaves or other litter will help the fish settle.
Make sure there are at least 12 – 14 hours of dark so they are able to sleep and keep the times the same every day as fish like us get used to bedtime. So turn those lights off at the same time each day maybe get a timer to do it for you.
Fish Do Sleep conclusion
Hopefully, we’ve learned that fish do indeed sleep. Much like us, they need to sleep every day normally at night to keep themselves in their natural rhythm. We’ve also discovered that fish slow their metabolism down including their breathing. This allows them to heal and recharge while sleeping and not use any excess energy.
Also, we know now fish can dream this has been observed via research labs and in the wild. Using brain wave patterns and electrodes as well as observing. For instance, octopuses usually change color when finding prey or escaping a predator. Well, we now see them change color while chilling on their own it’s now believed to be dreaming.
All in all, there are some exceptions but I think we can all agree fish do sleep. I hope you enjoyed the read and please feel free to take a look around the site for more great articles.
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