Do Fish Act Dead? Why do They Float Upside Down?

Imagine waking up one day and discovering that your cute little goldfish is floating upside down. Is it dead?

With your heart in your throat, you lunge forward, only to discover that it has straightened itself and seems to be floating just fine!

Yes, this is exactly what I experienced a few days ago when I bought my very first pet fish home.

And this led me on my journey of research on whether fish act dead and why they float upside down. Here is all that I found out.

Fish do not act dead! If they are floating upside down, have swelled up like a balloon, or even swimming erratically near the top of the water surface, it is an indication of something being wrong. It is called the impaired buoyancy that occurs because their swim bladder isn’t working properly. Swim Bladder Disorder makes your fish lose their ability to swim properly.

The question is, why is it that your fish may have developed a Swim Bladder Disorder? Are they ill? What can you do to help them out?

Trust me, I have researched it all, so you won’t have to. Read on to find out more.

Why Do Fish Float Upside Down (Video)

Do Fish Act Dead?

This is the first part of our blog. Can fish, like humans, act?

The simple answer to this question is no. They simply are not dramatic, or for that matter, intelligent enough to want to make a fool out of you. Fish don’t act, let alone act dead.

If they are looking weird, seem to be floating upside down for long stretches of time, swimming erratically, or showing their belly more than necessary, then it means there is something wrong with them.

They are either ill, have a short supply of oxygen, or their water tank has become too dirty.

Therefore, the first thing you need to notice is why your fish is acting all strange. Start by understanding your basic fish life and needs.

If you are a new pet fish owner, then there are quite a few things you may not know.

Some of the most common strange fish behaviors that could be a sign for you to make some changes or take them to the vet:

  • Listlessness: Does your fish seem like it is listless and dull? The first thing to check is the temperature of their water. If the water is too cold or too hot, your fish will become inactive. Overfeeding in another cause of lethargy, so reduce the amount of food you have been giving to see if it works.
  • Erratic swimming: Erratic swimming isn’t always a sign of alarm. Fish sometimes play or exercise by swimming in a manner different than normal. But if this behavior continues for too long, then you will need to check the quality if their water. Is the pH right? Too many nitrates or ammonia? Improve the quality of the water and your pet will become fine. Other times, erratic swimming can either be a sign of illness or the presence of external parasites.
  • Gasping: This is a clear sign of a lack of oxygen. When you see a fish coming up to the water surface and gasping for air, it means the tank does not have enough oxygen for them. Either clean the tank or get an aerator for them.
  • Hiding: This is very normal for a fish, as they consider it a form of play, or simply are not comfortable yet in their new home settings. So long as they remain comfortable and healthy, you don’t have to worry about anything, because they will start showing more of their face in a few days.
  • Sitting on the bottom: This could be perfectly normal behavior for some fish, like the catfish. They are known as bottom feeders and prefer to stay on the base of the fish tank or aquarium. Many fish also like to sleep on the bottom of their habitat. Of course, if this behavior is new and is combined with listlessness and erratic swimming, then your fish may be coming down with something or is already ill. The best approach at such a time is to quarantine your fish. They are probably suffering from swim bladder infection and by getting them to fast for a day, or giving them easily digestible food like peas will help. Also, be sure to check the quality of the water they are in.

These are the most common fish behaviors that scare people. Which one of these is our fish acting out?

Once you have found the cause of your fish behaving strangely, try to minus out the factors leading to such behavior.

If things still don’t improve, get in touch with a vet.

Why Do Fish Float Upside Down?

This is the most important thing you need to understand, is why fish float upside down and then seems to get back to their normal life routines.

It is a fact that when fish die, they flop over and become bloated. This happens because decomposition fills up the fish’s stomach with buoyant gases. These not only distort their features, it also causes them to bloat and results in their floating belly up.

Another reason why fish go belly up is that their spine is heavier as compared to their bellies, which means the spine goes downwards because of gravitational force.

Do Live Fish float?

They do when they are feeling ill. But this is only a temporary situation. It doesn’t last for long, and they get upright again before swimming away.

Still wondering why it is that live fish does not float? Let’s look at it biologically.

A fish is made up of bones, water, fat, protein, carbohydrates and nucleic acids. Even though fat is denser than water, a fish contains more amount of bones and proteins as compared to fat, which allows this animal to become neutrally buoyant in water.

This means it neither sinks down nor floats on top of the water. Some fish are denser than water, which allows them to go down and come up as they please.

What is the thing that allows them to swim deeper or come up in shallow waters without drifting away?

They have an organ that is called the swim bladder or air bladder. This is what aids in regulating their natural density, which then lets them swim with ease. It works by passing water from the fish’s mouth through its gills.

This does not just let the fish gain access to oxygen, as humans do with lungs, it also helps them in keeping their buoyancy. This also means that the pressure on and around the fish is maintained through this mechanism of the swim bladder.

Now you know how the fish is able to nether drown, nor float on top of the water, but swim as per it’s needed.

The Phenomena of Live Fish Floating: Swim Bladder Disorder

So why is it that your fish is acting out of character and seeming to float while it is still alive?

Here is the answer for you.

Impaired buoyancy is what causes a live fish to float on top of the fish tank. This happens when their swim bladder isn’t working as it should.

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The condition is known as Swim Bladder Disorder and it takes place because some kind of illness is not letting the organ work properly, get fully oxygenated blood to the bloodstreams of the fish and swelling up their bodies, causing them to float.

Your fish will lose control of their body movements and would be turned upside down, as they get closer to the surface of the water tank. Keep in mind, all this happens while your fish is still alive.

The most important thing you need to understand is that this is not an indication that your fish has died. But it is a clear sign of come underlying problem.

This is the reason that even though swim bladder disease is not fatal on its own, you still need to immediately start treatment of the disease-ridden fish.

If you don’t take precautionary measures, then you will lose your beloved pet in a short span of time.

Why Does Swim Bladder Disorder Occur?

The disorder takes place either temporarily or permanently. It happens because of a number of reasons like swallowing too much air, some kind of bacterial infection, pressure from a swollen body or even some kind of injury.

The disability of the swim bladder means the fish will not be able to function properly and its swimming will become off.

In order to find out exactly what is wrong with your fish, you will need to find out the underlying cause of the disorder.

Is it too much food or some illness? Injury or lack of oxygen? Once you have been able to find the real cause, solving the issue will become easier.

Some Common Causes of Swim Bladder Disorder

Here are some of the most common reasons why swim bladder disorder takes place and what you can do to improve the condition of your pet fish.


This is one of the most common causes of swim bladder dysfunction. What happens is that when your fish is constipated, it presses the swim bladder, which means not enough space to function properly.

The good news is, it is also the easiest to treat.

According to some people, it is best to make your fish fast for a day.

But according to most experts, in order to reduce the constipation of your fish, you need to feed it better, meaning, feed it a rich source of fiber. Fiber will be able to cleanse the digestive system of your fish and help it in overcoming constipation.

Here is how you can best treat a fish suffering from constipation that has developed the swim bladder disorder:

  • Take some fresh or frozen peas, and thaw them. Once they have defrosted completely, boil the peas, but be sure to not overcook it.
  • Make sure to peel the skin off as you only need the meat and not the peel for your fish. Mash the boiled and peeled peas so that it is easier to feed to your fish.
  • Once the peas have been mashed, feed them to your fish by hand. Be sure to not overfeed as that can further disrupt their digestive system.
  • After the peas have been consumed, let your fish be for the next 24 hours. There should be no other feeding within this time frame.
  • Be sure to clean the fish tank once all feeding is complete. The last thing you need is an increased amount of ammonia in the tank that takes place because of rotting food. This will only further irritate the digestive system of your pet fish.

Within 24 hours, your fish should start feeling and acting better. Their bellies will lose the swollen up feel, the bloating will go down and you will see an improvement in their activity level too.

If you feel that there is a decrease in their appetite and they are refusing to take the boiled mashed peas, then you are left with no choice but to let them fast. Let them be for no more than 3 days.

Make sure the temperature of the water is somewhere between 72 to 80 degrees F. This temperature allows the intestines to warm up and improve metabolism.

Try giving them peas after the 3 day period and let them fast for another 24 hours. Your fish will gradually return to their normal, happy self.

Bacterial Infection

The bacterial infection is another cause of swim bladder disease. What happens is that bacteria lads to the accumulation of fluid being filled in the bladder. The infection can be detected through an ultrasound.

This infection can either be the result of spoiled water or some kind of bacteria caught from the environment. Keep in mind that this infection can also occur because of a change in the season.

You can only find out the actual cause and presence of the infection through a process known as pneumocentesis. It involves putting a needle into the bladder and taking fluid out. This fluid is then tested for the kind of bacteria present.

Once the real cause of bacteria is known, your fish can be treated properly with antibiotics. The one most important thing you need to keep in mind is that you can’t start an antibiotic treatment on your own. It has to be recommended by the vet after getting the fluids tested. Most commonly given antibiotics include Minocycline or Erythromycin. 

If the swim bladder disorder is due to the water quality of the tank, then antibiotics must be avoided. Remember, if antibiotics are misused, they can cause harm o your pet.

Before you make the hasty decision of giving antibiotic to your upside down floating fish, keep in mind that there will be symptoms other than just the erratic swimming. Your fish might lose its appetite, become stiff or even have uncontrollable shaking.

The best way to keep your beloved pet safe from bacteria and from pathogens developing in its tank is to get a UV sterilizer.

Swallowing too much Air leading to Bloating

Yes, a fish can literally swallow too much air. This mostly happens when you feed non-sinking food to your fish, as the greedy little thing eats more than it should. This gives way to a bloated swim bladder and hence disrupts the buoyancy of your fish.

The best way to treat this condition is by giving your fish the boiled peas. They will get rid of the gas easily.

Deformation of Swim Bladder

If you have a goldfish or betta, then the chances of seeing a swim bladder disorder are common. The reason is that these fish have been a product of genetic selection, which is why they are so appealing to you in the first place.

Selective breeding also leads to some physical deformations. Hence the reason why betta and goldfish are more susceptible to swim bladder disease.

The sad part is, if the problem is there due to birth deformity, there isn’t much you can do. You can only give them love until they last.

Of course, this will only be diagnosed once you visit the vet, so it is important to do so the instant you notice your fish going upside down near the surface of the tank.

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Physical injury or damage can be a result of fish fighting with each other or while they are transported from one place to the other. Something in the tank can also lead to injury.

In most cases, if the swim bladder has been damaged beyond repair, you can’t do much more than providing a comfortable last few days.

You can also talk to the vet about alternative ways to help ease the pain your little pet is in.

High amounts of Nitrates

Many new pet fish owners don’t know how hazardous a dirty tank can be. The neglected water can become extremely dangerous for your fish’s swim bladder, as it can lead to a variety of infections.

Particularly if you have a goldfish, you need to understand how messy they can make their aquarium. They are prone to high amounts of poop as compared to other fish. Hence the reason why you need to change the water more frequently.

If there are too much waste products in the water, be it from the fish or rotting food, it could lead to high doses of ammonia. Ammonia then converts into nitrites (NO2), which in turn converts into nitrates (NO3).

According to research, high doses of nitrates causes an increase in the risk of a swim bladder disorder.

The best way to make sure your fish does not catch infection because of nitrates keep changing the water regularly.

What’s more, you will need to change the tank of the ill fish by putting them in a larger tank.

Also, remember that nirtates can accumulate in the filters, so you should be cleaning them regularly as well.

There is another thing you have to pay attention to, the amount of water you change. If you change the whole water too often, it could mean that the good bacteria that your fish needs for survival have also gone out with the bad bacteria.

This is why you should only change 40% of the water in a large tank and even less in smaller tanks.

The addition of plants in the tank will also help in controlling the number of nitrates and keep the habitat of your fish just like it should be.

Avoiding the Development of Swim Bladder Disorder

So what is the best way to avoid swim bladder disorder among your fish? Here is what you can do:

  • Never overfeed your fish. Keep in mind that your fish does not understand the idea of overeating and will keep eating the more you give them. You will have to be the one to stop. Too much food causes bloating, which in turn presses against the swim bladder resulting in the disorder. An automatic fish feeder is your best friend to avoid the disease and save your fish from untimely death.
  • Overfeeding leads to contamination of the tank, not simply because of food remains, but also because of excessive pooping. This means more nitrates and hence the greater possibility of swim bladder disease.
  • Do not give too much food that floats on top of the surface. This way, your wish will gulp more air than it needs and will end up with a bloated tummy. Again, swim bladder disorder. Opt for sinking food as much as possible.
  • Food that has porous texture also fills up your fish’s stomach with gas. Avoid giving it.
  • If you have dry food for your fish, soak it before giving it, as that would not expand in their little tummies, leading to bloating.
  • Water changes are essential, as regularly as possible. This will keep the environment of the tank clean.
  • Invest in a large filter as that will let the tank have more beneficial bacteria. It will improve the biological filtering and reduce the chances of developing a bladder infection.
  • Keeping just the right temperature in the tank is also essential. Thy generally needs warm water to keep their metabolisms working up to par. If the water becomes too cold, it will slow their digestive system and cause constipation.
  • Once every week, it would be ideal to give a fibrous diet to your fish. Be it pea or some commercially produced food, just ensure that it is rich in fiber.

These few details will help in keeping your fish healthy and happy, without feeling the need to float upside down.

Frequently Asked Questions

How to Tell if a Fish is Dead?

If your wish has been floating upside down for long, then you need to consider the though that it might be dead. This happens, because you can’t save them every single time once they have developed a swim bladder disorder.

Be prepared for the worst and be willing to part with your beloved pet. Once the fish is dead, you will need to look at them carefully. Do their gills move? Are their eyes moving? If not, then they are probably gone.

A dead fish also begins to lose its color. If it has started turning white, that is a sure sign of death.

You can bury it in your garden, or put it in a plastic bag and throw it in the garbage.

Be sure to remove the dead fish as soon as possible, because the decomposing fish can contaminate the water and make survival difficult for other fish in the tank.

Why Do My Fish Keep Dying?

The most common cause of fish dying is overfeeding. As mentioned before, fish do not understand the concept of eating more than their limit, which is why you will need to be the one to monitor this.

For example, if you have betta, they only need three of those micro-pellets for them to feel full for the whole day. Any more than this and it will come under overfeeding.

The second most common cause of fish dying is the environment they live in. Do you clean the tank enough? Aerate it? Changing the water? Keep in mind that your fish do not have separate toilets to go potty, which means they do everything in the same water that they breathe in. Hence the importance of keeping their tanks or aquariums clean.

Temperatures should be on the warmer side for most fish as they are cold-blooded and need a warm climate to be able to metabolize their food.

So long as these things are monitored, your fish should live a long, healthy and happy life.

Do fish always float up when they die?

Yes in most cases, but not always. There are some fish that will sink to the bottom of the tank when they are dead and will need to be checked to ascertain that they are dead. If the swim bladder is not filled with gas, the dead fish will sink. Be sure to check the fish for other signs before declaring it dead.

Now you know how fish don’t act dead. They float upside down due to the malfunctioning of their swim bladder either because of injury or some kind of illness.

Now go give some attention to your little buddy and take them to the vet if necessary. Good luck!

Photo of author

Nadine Oraby

My name is Nadine; I am a passionate writer and a pet lover. People usually call me by the nickname “Joy” because they think that I am a positive and joyful person who is a child at heart. My love for animals triggered me to create this blog. Articles are written by vets, pet experts, and me. Thanks for visiting. Your friend, Nadine!

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