The biological functions of a fish’s body are vastly different from those of mammals. Because of this, many pet fish owners are unfamiliar with how exactly a fish’s internal organs are able to function. There are many differences between fish and humans, most notably including the fact that fish are able to ‘breathe’ only while immersed in water. A question that many fish owners commonly wonder about is if, in fact, fish are able to sleep. The answer to this question is: Both Yes and No. Fish do not sleep in the way that most of us humans commonly define sleeping, though fish do have a specific pattern of activity with periods of rest.
DEFINITION OF SLEEP
Humans spend approximately eight hours per night sleeping, which equates to about one third of the time of an average human life. Human sleep consists of a period in which our heart rate and breathing decreases, muscle relaxation occurs and a deep ‘hibernation’ period occurs. According to the Saunders Comprehensive Veterinary Dictionary, sleep in animals is generally defined as “… a period of rest during which bodily functions are suspended and diminished sensitivity to eternal stimuli”. Most pet care experts agree that many animals experience ‘sleep’ in different ways. In fact, it’s been confirmed by some fish care specialists that the brain waves of ‘sleeping’ fish support the fact that fish do not experience sleep in the same way as some higher vertebrates.
SLEEPING FISH
It’s generally accepted that fish have a designated period of ‘rest’ in which their awareness of their surroundings substantially decrease. However, fish do not enter a period of unconsciousness in which they are completely unaware of the world around them. The brain waves of most species of fish are unchanged during periods of ‘rest’, which means that fish do not experience REM sleep. During this period, the fish may drift with little or no fin movement around the bottom of the tank. Most ‘sleeping’ fish rest on the bottom of the tank, though are easily roused from their period of rest if subjected to external stimuli.
HIBERNATING FISH
Certain species of fish have a sleep cycle that is mostly attributed to hibernation. During this period, a fish will enter a sedentary state, in which their metabolic rate greatly decreases. This also results in a slowing down of all of a fish’s bodily functions, though this is not as drastic as the type of hibernation experienced by certain mammals. Hibernating fish sometimes retreat to a small shelter, or may simply reside in a low area of their water habitat.
DORMANT FISH
There are some special species of fish that enter a period of estivation during dry seasons in order to prevent from becoming dehydrated. This is an extremely interesting phenomenon, since it allows a fish to essentially survive outside of water for a period of drought or extreme heat. In Africa, there is a species of fish that cocoons itself inside a casing of mud in order to spend several months in a dormant state. This is similar to the behavior of Carp, who bury themselves in mud during the cold winter months in order to prevent themselves from freezing.
19 Responses to “Do fish sleep”
dan i just got a 1.5 gallon of a fish tank
I was wondering if it depends on the type of fish for it to sleep. Any body know?
I just got a 1.5 gallon fish tank, and I have quite large pebbles and I bought a glow fish and it died the next day
so then I bought two tetras. And I don’t know if when they go to sleep if the rocks will crush them, because I think that is what happened to my glow fish. Any tips???
i have a betta fish he sleeps in a rock cave i bought him
should i turn my tanks lights off in the night for the fish to sleep?
Yes I would. I have a Betta fish and he does not seem to like it when the lights come on when he is resting in the bottom of the tank
Gustavo! You need to get rid of the Bala shark! Now! Unless you wanna invest in REAL big tank, either give him to someone who has a big tank or take him back to the store. (But don’t expect any money back. It doesn’t work that way.). Then buy AT LEAST a 10 gallon with a flourescent light for your other specimens and, at that point, you can even add a couple more SMALL fish. And please slap whoever sold you the Bala, find a knowledgeable fish store employee to advise you and remember this rough guide t
Gustavo (Part 2) A rough guide to the number of fish you can have is one inch of fish – grown – for every gallon your tank holds APPROXIMATELY. But the shark needs a new home, period. And make sure you do a partial water change every week or so. Take out, and replace, approx. 1/4 to 1/3 of the water using chlorine treatment if it’s city water. And NEVER “break-down” the tank. Ask that knowledgeable employee you’re gonna find how to do and happy fishkeeping to you!
u can put few males togather IF and only IF the area or size of your aaiuruqm is BIG enough .. they fight each other because they have no space to avoid the battle , so fight to death is their only hope . better keep them on a 14inch radius distances to each other so they won’t need to fight for a territory ^^
we now have 1 bala shark,1 tetras, and 2 tiger barbs in a 1.8 gallon tank and we turn off their lights at night
Gustavo a bala shark needs a 50+ gallon tank. you can have a 40 but it must be long, bala sharks can reach 18 inches in adulthood, so they need a big tank. how big is your bala shark? when its large enough it will eat your tetra, i learned the hard way. i had a bala shark and 15 tetras. now im down to 3 tetras curiosity to my bala shark
We just purchased our first fish tank together. We are so excited. we bought several gold fish of all sizes and we bought some zebra danios an angelicus and MY PICK the rainbow shark. The angelicus is sooo aggressive and we thought it was going to be the shark, guess not!! lol Anyway we are looking forward to seeing them sleeping and watching them grow.
I have cat fish.at night they all settle at the bottom of the clean water without body movement.are they not sleeping?
I have a black ghost knifefish…he resembles an eel. I often see him lying on the bottom of the tank much like my other one did before he died, but when I tap the tank he wakes up. He seems to be completely fine. I am unsure if he is sleeping or could be sick? Any fish sleeping experts have an answer?
Yes , My name is professor Smichel. It is good that you tap to wake them up but fishes
wake up a 9.00am so wait to get them up in the morning
thats so stupid because fish are pretty much always alert so they shouldnt have to be woken up.? i totally disagree.
I also have a knifefish and he does the same exact thing their naucturnal only active at night. Turn the lights off and watch it he will be all over the tank
I have a beta fish and he sleeps on the large leaf of the silk plant I provided for him.
I have a salt water aquariem with some fishes in it. I have a Queen Wrasse fish. that hibernates it self be enters in to the Coral sand at about 8:30Pm and comes out at 8:30 Am.