Cause (+ Cures) for a Fish That’s Floating Upside-Down But is Still Alive?

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Witnessing your beloved pet fish swimming upside down can be perplexing, sparking a flurry of questions about its health and well-being. If your aquatic companion exhibits this unusual swimming pattern, it clearly indicates underlying issues. Understanding the root causes behind this condition and implementing timely treatment measures are crucial for restoring your fish’s vitality.

Goldfish swimming upside down
Goldfish swimming upside down

One day you wake up to the stunning sight of your favorite goldfish acting like a balloon.

A fish floating at the top of the tank but not dead yet (even actively moving around) can be confusing to witness. What does that signal?

What about the other way around — your fish is swimming upside down but hangs out on the bottom?

This can happen to almost any fish species, not only goldfish.

Truth to be told if you find your little buddy swimming turned belly up, then its condition has probably been around for a while now.

The initial stage can be detected when you notice sideways or even nose-down-tail-up swimming. Any form of fish imbalance is considered a potential threat to its health.

Why is your fish hovering upside-down, but still seems alive and active?

If a fish displays such behavior it means that it has buoyancy issues. If that happens then you’d need to react on time and start treatment immediately.

Here’s the reason behind a fish that floats upside-down, yet remains alive:

The impaired buoyancy in fish is caused by a malfunction of their swim bladder. When affected by Swim Bladder Disorder fish will often lose the ability to swim properly. They will float uncontrollably to the top of the aquarium, turned upside down, while still being alive.

In some cases, the fish will lie upside down or sideways on the bottom and be unable to swim upwards. Affected fish will face difficulties maintaining their floating balance, as the swim bladder is located in the lower half of the body.

The swim bladder disease in fish is not lethal on its own and it is instead a symptom rather than an independent condition.

Why is my fish swimming upside down?
Why is my fish swimming upside down?

Note that in some fish such as the upside-down catfish swimming with the belly up is a typical trait of character.

What causes swim bladder disease?

A swim bladder malfunction is caused by a temporary or permanent deformation of the swim bladder. When it is deformed or narrowed in some way, the fish loses the ability to balance its body, while swimming.

The reasons behind that can be the pressure from a swollen belly, too much air swallowed, injury, or bacterial infection.

In addition to these reasons, fatty deposits in the liver, kidney cysts and egg binding can also affect the bladder and lead to buoyancy issues.

In some fish, low water temperatures can enlarge the gastrointestinal tract by slowing down digestion. For the aforementioned reasons, this also puts the swim bladder under pressure.

Sometimes after eating too much a fish may gulp some air on purpose, to regulate its buoyancy.

To cure your fish you need to investigate the reason for its bizarre behavior.

You should treat it accordingly after you estimate the nature of the problem, ideally through your local veterinarian.

How to treat the different conditions that cause your fish to swim upside down?

Swim bladder disorder
Swim bladder disorder – Image by ExoS

Relocate your pet fish to a hospital tank immediately after noticing the odd behavior.

This way you’ll have more control over the treatment without affecting other fish. All food or medication will go where it belongs – in your ill fish.

Sometimes the treatment requires days. Be sure to check the water parameters and maintain healthy water quality in the recovery tank.

That being said, here are the reasons behind swim bladder disorder and how to treat them:

#1. Treating constipation that results in a swim bladder malfunction

Swim bladder malfunction
Swim bladder malfunction – Image by Training-Gap-5728

This is a manifestation of a swim bladder disorder that’s relatively rare. Fortunately, it is the easiest to treat. Constipation will cause a bloated stomach, which will press against the swim bladder.

A good approach would be offering your pet fish a specific food source that’s fiber-rich.

The fiber will force everything out of your fish’s digestive system.

Here’s how to treat swim bladder disease caused by constipation in your omnivorous or herbivorous fish such as goldfish and the like:

  1. Thaw a frozen pea. It is better to leave the pea to thaw naturally. However, as this disease’s treatment can be time-sensitive , I recommend microwaving it to the defrost function.
  2. Boil the pea. Cook the pea in boiling water while being careful not to overcook it.
  3. Peel the skin off of the pea. The pea skin may cause swallowing complications for fish. You need the meaty insides of the pea for the treatment.
  4. Soak the pea in water. This is done to avoid swelling of the pea inside of the fish’s stomach. Mind that the cooked pea will sink, so use a shallow container for the soaking.
  5. Feed your fish the cooked pea. Hand-feed the pea if needed. The fish will have difficulties getting the food. This is where the hospital tank comes in handy.
  6. Skip feeding in the next 24 hours. Let the fibers in the pea do their job at helping your fish with digestion.
  7. Clean off any leftover food after the offering. Hospital tanks are usually smaller. The water will quickly become dirty. A sudden ammonia spike, caused by rotting food is the last thing you’d want in a small tank.

This is the best-case scenario for constipation treatment.

The belly of the fish will lose volume, allowing for the swim bladder to function correctly.

Another good source of fiber for treating constipation, especially for a carnivorous fish such as a Betta, is Daphnia.

At times Daphnia can be somewhat difficult to find in your local fish store, but you can find it in better online stores for aquarium supplies such as Amazon (or just click this link).

Anyhow, sometimes the fish may also experience a loss of appetite.

In this case, you have no other option than to starve it. Fast the pet for 3 days.

Cold water slows down the metabolism of fish, which slows down digestion. During fasting, most fish will do well at a water temperature of between 72 and 80 °F (22 to 26.6 °C). This way the intestines will have the needed time to digest the hardened food.

On day 3 you should feed the cooked pea. Again, fast your fish for another 24 hours after that.

To avoid future bloating issues, you should diversify the fish’s diet. But more on that below.

Constipation may also be caused by food that’s swelling inside your fish’s tummy.

Monitor the fish’s stools: if they do not properly leave the body and hang from its rear for a couple of seconds, then that’s a clear sign of a constipated fish.

#2. Bacterial swim bladder treatment

Bacterial swim bladder treatment
Bacterial swim bladder treatment – Image by King_Maoyu

How to kill bacteria in the swim bladder of your fish:

Sometimes swim bladder disease is caused by a bacterial infection.

This will result in the bladder being filled with fluid.

Research shows that sometimes, swim bladder inflammation can occur with seasonality.

It can be estimated that the bladder holds liquid with an ultrasound diagnosis.

If liquid is present, the infection is either from spoiled water quality or bacteria.

The only sure way to confirm the cause is by a method called pneumonectomies.

Essentially, it involves sticking a needle directly into the bladder and testing the fluid for the type of bacteria causing it.

Knowing who the offender is, proper antibacterial treatment can be applied.

However, in their panic, most aquarists start treating the ill fish with numerous antibiotics.

If the issue doesn’t come from bacteria, but rather water quality, it’s strongly recommended that antibiotics be avoided.

The misuse of antibiotics will cause more harm than good to a fish’s immune system.

However, if you did measure the water parameters and are confident they’re not what’s causing the condition, using a broad-spectrum antibiotic is your best bet. Minocycline or Erythromycin are good examples.

Of course, your best course of action is to take the fish to the vet.

When an infection is present the fish will display other symptoms alongside swimming upside-down.

There may be a loss of appetite, stiff fins, and uncontrollable shaking.

Note that to keep your fish safe from harmful bacteria and other pathogens you should consider getting a UV sterilizer.

#3. Bloating from swallowing too much air

Fish bloated after swallowing too much air
Fish bloated after swallowing too much air – Image by Paul Bradford

In a fish, there are actually two sacks acting as swim bladders. The larger one of them is directly connected to the stomach.

Whenever you feed non-sinking food you risk greedy fish gulping too much air while having their feeding frenzy. This may lead to a bloated swim bladder and therefore a disturbed buoyancy.

In this case, a boiled pea treatment will suffice.

#4. Birth deformation of the swim bladder

Birth deformation in Betta fish
Birth deformation in Betta fish – Image by hweeheng

Sometimes, the reason for a malfunctioning swim bladder can be a birth deformity:

The swim bladder disorder is mostly seen in goldfish and bettas. Although a betta laying on its side could mean a number of things (click the link to see those explained), in goldfish it is not the case.

These two particular species have been continuously bred over time, to achieve aesthetic diversity.

The beautiful fish you see at fish stores result from genetic selection.

However, with selective breeding come physical deformations.

This is why it’s so common to see these two species suffering from swim bladder issues (with goldfish holding the lead).

If a birth deformation is causing issues in your fish’s swim bladder, little can be done.

You will need to apply special care, to ensure your fish leads a happy life.

But, in time the condition will worsen and eventually turn lethal.

Often if the SBD is the result of a birth defect, symptoms are present at an early age.

An easier diagnosis is somewhat a relief because no further investigation is needed.

Another untreatable condition that will suppress the swim bladder is the development of tumors.

Your fish may have cysts growing in its kidneys, which will enlarge.

#5. Physical damage or injury

Physically damaged fish swimming on its side
Physically damaged fish swimming on its side – Image by ghooda

A high drop, engaging in a confrontation with other aggressive fish species or other mechanical damage can cause SBD:

If the swim bladder has been damaged by an injury, say, during transportation, there’s nothing you can do about it.

If your fish has just arrived and is being this way, without improvement from previous treatments, it is probably a goner.

It’s really sad, as these cases happen on occasion and there’s nothing that can be done.

I recommend considering a humane way to euthanize it.

You will spare it from suffering a slow and unpleasant death.

#6. Poor aquarium water quality (high nitrates)

Test your aquarium water for poor quality indicators
Test your aquarium water for poor quality indicators – Image by isabelablue

Neglected water conditions may very well be the reason for an infected bladder:

As mentioned the disease is often found in goldfish. Aside from selective breeding, there is another reason for that.

Goldfish are known to make a mess in an aquarium. They poop way more than other fish of their size. Therefore they would need more gallons of water per fish than with others.

Unfortunately, this is often overlooked by new fishkeepers.

Significant amounts of waste will result in ammonia spikes.

The ammonia then converts to nitrites (NO2), which become nitrates (NO3).

Research has shown that high levels of Nitrate in the aquarium can be related to swimming bladder infections.

Here’s a visual diagram from the research that shows the correlation between side swimming and high nitrate levels in the water:

High nitrite levels correlation with side swimming
High nitrite levels correlation with side swimming

In fact, if a fish has swim bladder issues, it’s a strong sign that Nitrate poisoning is on the way.

Long-term exposure to nitrate levels of even 20 ppm (parts per million) can cause this.

Note that using a liquid water test kit is somewhat mandatory when accurately assessing the water’s parameters in your aquarium. Test strips can be quite off and only give a crude estimation of the actual Nitrate levels in the fish tank. Make sure to use a liquid test proven to take accurate measurements. I recommend using this or a similar one as it has done well for me so far.

Anyway, after constipation, nitrate intoxication is the second most common reason for sideways or upside-down swimming in fish.

To treat SBD in this scenario perform a change of up to 40% of the aquarium water over the course of a day, depending on the level of Nitrate. You’ll want to bring them down to about 15 ppm or less. To avoid causing further chemical shock to the fish only remove 5% to 10% of aquarium water per hour. Relocate the ill fish to a larger tank as soon as possible.

If you can’t provide more gallons of water,  be consistent with the water changes or learn how to permanently keep the Nitrate at safe levels.

Nitrate-causing gunk can also build up in the aquarium’s filter, so change/rinse it as needed.

If your fish experiences upside-down swimming after a water change, this may be a sign of environmental stress.

Sometimes after a huge water change that’s done at once (40% to 50%), the fish will start to breathe heavily and swim upside-down.

Even if only one fish displays the symptoms, it’s a strong confirmation of stress.

Removing too much nitrate ions from the aquarium water at once could impair a freshwater fish’s osmoregulation.

Osmoregulation is the ability of a fish to maintain osmotic pressure in its body fluids. An imbalance in that pressure could cause swollen organs and a malfunctioning swim bladder in aquarium fish.

Though nitrate is toxic in the long run, fish adapt to its presence to a degree. In the case of a nitrate poisoning event, you should remove the nitrates gradually to avoid further worsening the swim bladder condition.

Usually, in smaller tanks, there are not enough plants to control the nitrate levels, which can lead to an infected swim bladder.

#7. Fast the fish for a few days

This could be a good course of action if you’ve confirmed through a vet that your fish is constipated or has something that does not pass in its stomach.

If the swim bladder disease is caused by an enlargement of the gastrointestinal tract, you’d want to start the treatment by putting your fish on a three-day fast.

The lack of food will prevent any further blockages of the intestines and stomach.

Meanwhile, you’d want to increase the temperature of the water to 78 – 80°F and leave it at this temperature until the end of the treatment.

This will relax the intestines and reduce the swelling.

Finally, if your fish is carnivorous, such as a Betta, you’d want to give it a few pieces of frozen, freeze-dried or live daphnia during the fast.

The daphnia will act as a laxative that will push out any food matter blocking the gastrointestinal tract.

Author’s note: A short fasting is the easiest course of action when your fish has constipation issues. However, from what I’ve seen, constipation is rarely the cause ofupside-down swimming in pet fish.

Efficient ways to prevent swim bladder disorder in the first place?

Prevent swim bladder disorder

Do these to ensure your fish willnever have to face swim bladder disease again:

  • Avoid feeding floating foods. Pellets or other food that floats at the water’s surface encourages gulping air.

    Too much air in the belly of a fish can end up in its swim bladder. This will violate the balance and cause buoyancy issues.

    Feed sinking food if possible.

  • Avoid feeding air-filled foods. Some types of food will be more porous in texture than others. This introduces unwanted air in the fish’s stomach.

    The air from the stomach may get into the swim bladder and enlarge it.

  • Soak foods before offering. By soaking dried foods in water before offering you allow them to expand.

    This will prevent eventual expansion inside of your fish’s belly.

  • Thaw frozen foods. Whenever you offer a frozen meal, it should be fully thawed. These foods will gain volume when thawed.

    If this happens inside of your fish, it will lead to bloating.

  • Perform regular water changes. As much as this goes without saying, I am still obligated to mention it.

    Water changes will keep the nitrates in the aquarium in check, preventing potential bladder infections.

  • Buy a large filter. The bigger the filter – the more beneficial bacteria your fish tank will house.

    The more bacteria, the stronger the biological filtration, lowering the chance of bladder infection.

    Canister filters are the most spacious so far. Here’s a list of those.

  • Maintain the water temperature. Fish are cold-blooded creatures.

    This means that their metabolism is strongly dependent on their body’s temperature. Colder water will inevitably slow their ability to digest food efficiently and on time.

    This can lead to constipation.

    If you have a small tank check my guide on some of the smallest and yet reliable fish tank heaters.

  • Diversify the diet of your fish. Once a week feed your fish high-fiber foods.

    It could be a pea or any other fiber-rich source of food your fish will be willing to eat.

    Another way to prevent SBD is by occasionally feeding your fish bloodworm.

  • Avoid ball-like fish. The fancy goldfish is a good example. When stocking your tank avoid fish that are being bred to achieve a certain ball-like shape.

    In general, that’s most of today’s goldfish varieties.

Be mentally prepared for a grim ending

It is fairly important to point this out.

With swim bladder disorder there won’t be a happy ending every time. Usually, if the problem is caused by constipation the treatment is easy and efficient.

However, this is not always the case.

There are numerous factors that can cause this condition. A proper, yet timely diagnosis is not always possible.

Be prepared for everything.

My Conclusion

Swim bladder disease is a tricky condition to treat and I’ve personally fought it numerous times. In my opinion, the key to success is reacting in time.

Why are you still reading? Hurry up and help your fish buddy before it’s too late.

There’s always hope, even though an upside-down fish usually signals the opposite.

Poster - Why is my fish floating upside down?
Poster – Why is my fish floating upside down?

Leave me a comment below if you need more answers.

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Momchil Boyanov is the Founder and now Senior Editor of AquAnswers. He has over 13+ years of experience in keeping home aquariums as well as providing professional aquarium services. Momchil has had his fair share of adventures in aquarium care. He has made MANY mistakes throughout his fishkeeping journey and thus learned A LOT. Through Aquanswers, Momchil shares knowledge about freshwater and saltwater aquariums with the people within this community.

139 thoughts on “Cause (+ Cures) for a Fish That’s Floating Upside-Down But is Still Alive?”

  1. This is such a great article. Thank you for the tips. I’m dealing with the same issue in my 7 year old goldfish. He’s truly a part of our family and it’s awful watching him float uncontrollably in the tank. I’m praying that the remedies help him!!

    • Hi Crystal,

      Thanks for your kind words. I hope your goldfish buddy makes it through safely.


  2. One of our koi fish jumped out the pond… we found it later in the day but it was quite dry we swirled in around in a bucket of water for a while & it seem to regain some life it is now swimming a little but keeps turning on it side & it’s scales look a little damaged… Any suggestions to help it recover?

  3. I have a ryukin goldfish and have been treating her with epsom salt and melafix. I mash peas up and feed her with a tube but she is still upside down and has been for 5 days now. I put her in the big tank for 10 mins per day and change 1 third of her water. How long can they live upside down for? She swims around in the big tank ok until she flips over and doesn’t have the energy to flip back again. I then put her back in the hospitsl tank. I help her to stay upright throughout the day.

  4. oscar fish two years old two weeks not eating any thing change every thing use epsom solt water treatment now site down the tank i donot know what the my next step treatment the oscar fish email s.majestly AT live DOT com: please any advice

  5. I have male guppies one of them started looking bloated so I removed him. He is currently in a 1 gallon tank will my other 3 guppies are in and 8 gallon. He is a pure white guppy and currently his bottom half is a tad bit red. He is so round you can see his heart beating and other organs. I just cleaned his tank and now he is laying upside down or like in a parallel position. He seems to be trying to burrow himself in the pebbles. I have no idea what’s wrong and he looks so sad. Is their anything I can do?

    • He passed away right after I wrote this comment he just had his funeral. Still wondering what happened though.

  6. I have an angel fish, it use to play tricks and swim upside down or do flips but this time it floats on its side. Only one side stays up towards the surface and is still super active so not really dying is the case. Does seem to look like an air pocket in its stomach, I called pet smart and they said frozen peas but that hasn’t seem to been working either. Any suggestions.?

  7. Hello! Youre article seems helpful, but I have a small question. How long does it take for SBD to kill? Im a bit worried about one guppy, and im sure its overfeeding, I’ve hand fed it a cooked pea and waiting for it to take action, how long can I wait without worrying about it dying?

  8. hello! i have a guppy who (i think) hit its head and can’t swim regularly, is there still hope?
    (it lost its appetite and is hiding a lot)

    • Hi there,

      From what you’re saying, the damage may be permanent. When a fish loses appetite things become concerning.

      I’m sorry.

      Regards, Momchil

  9. We had a small 8 gal tank with 2 glofish and a tiny sucker fish that sprung an awful leak all over our kitchen, so we had to change out everything. We washed the new plants and everything in what was left of the old water and tried to acclimate the fish to the new tank as best we could, using as much of the old water as we could (since it was still clean), and we brought the temp to match, but 2 of the 3 are now swimming like they are in little tornadoes. It started with one and now the 2nd glofish is as well. What can we do? I added clarifier to the water and a new water solution as well to help get out any “bad stuff” from tapwater…I’ve never had issues with changing out their water before.

  10. I’ve had my gold fish for 14 years now and he started having issues swimming it looked as if he was getting pulled down, he was also lying on his side at the surface of the water. I don’t know if it’s down to age or Buoyancy issues. He has been on the bottom of the tank the last two days on his side but breathing and moving to different areas every now and again.

    • Everything I tried didn’t work for my little guy. He got to where if I touched him he would go to the top then back down. Sometimes he would get stuck in the Bush decorations and I would have to help him out. He ultimately lasted 6 months and past after being stuck yet again in the Bush decoration.

      The three I had left did great but because they like to be in pairs the one who was paired with him seemed lonely so I got some more at Per Smart. One by one the ones from Pet smart died then the older ones that were 10 years old passed too. I felt like I killed them by trying to help there loneliness. They were definitely part of our family and was a great loss. My opinion is that maybe they do only have a certain lifespan and 10 to 15 years is a long time. Hope yours makes it through what its dealing with.

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