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

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

A fish floating at 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?

In fact, this can happen to almost any fish species and 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 as soon as you notice sideways or even nose-down-tail-up swimming. Any form of imbalance in fish is to be considered as 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 properly swim. They will float uncontrollably to the top of the aquarium, turned upside down, while still being alive. In some cases the fish will lay upside down or sideways on the bottom, unable to swim upwards. Affected fish will face difficulties when trying to maintain 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 rather a symptom than an independent condition.

Note that in some fish such as the upside-down catfish swimming with the belly up is a normal 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 a bacterial infection.

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

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

Treat accordingly after estimating the nature of the problem.

How to treat the different conditions that cause Swim bladder disorder?

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

This way you’ll have way 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

This is the most common manifestation of a swim bladder disorder. Fortunately, it is the easiest to treat. Constipation will cause a bloated stomach, which in turn will press against the swim bladder.

Many online sources advise that you should fast your fish to treat constipation.

However, a better approach would be to actually feed it. But you need to offer a specific food source – rich in fiber.

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

Here’s how to treat swim bladder disease caused by constipation in your fish:

  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 on 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 fishes’ 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 properly.

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 over the better online stores for aquarium supplies such as Chewy (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. Most fish will do well at a water temperature of between 72 and 80 °F (22 to 26.6 °C) during the fasting. This way the intestines will have the time needed 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

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.

Sometimes, Swim Bladder Inflammation can occur with seasonality, research shows.

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

If there’s liquid present the infection is either from spoiled water quality or bacteria.

The only certain way to confirm the cause is by a method called pneumocentesis.

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

With knowing who the offender is a proper antibiotical treatment can be applied.

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

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

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

However, if you did measure the water parameters and are certain 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 taking the fish to the vet.

When an infection is present the fish will display other symptoms along with 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

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 for greedy fish to gulp 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

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 today are the result of 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 there’s little that can be done.

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

Still, 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 its kidneys, which in turn will enlarge.

#5. Physical damage or injury

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 then it is probably a goner.

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

I recommend considering a humane way to euthanize it.

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

#6. Poor aquarium water quality (high nitrates)

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 then 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:

In fact, if a fish has swim bladder issues, it’s a really 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 that has been proven to take accurate measurements. I can recommend using this or a similar one as it has done well by 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 change 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 you can afford it.

If you can’t provide more gallons of water, then be consistent with the water changes or learn about ways 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 can be a good 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 it’s only one fish displaying 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.

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

Do these to ensure your fish would never have to face swim bladder disease again:

  • Avoid overfeeding. Providing your aquatic pets with too much food actually doubles the trouble:

    Fish do not recognize the concept of overeating. More often than not they will eat more than needed when offered.

    This may lead to a bloated belly, pressing against the swim bladder. One pinch a day should be more than enough. To never worry about dosing (and timing) you can just get an automatic fish feeder.

    One that really stands out is the Eheim automatic feeder unit. It works reliably and you will 100% not overfeed. Make sure you choose the right food, set it, and change the batteries every couple of months.

    That’s it.

    Oh, by the way, here’s a link to see the thing (at Chewy).

    Another outcome of overfeeding is water contamination.

    Leftover food will quickly break down into ammonia, oversaturating the aquarium’s beneficial bacteria. When this happens the fish tank will experience a nitrate spike that may lead to a swim bladder internal infection.

  • Avoid feeding floating foods. Pellets or other food that floats at the water 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 is housing.

    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 coldblooded creatures.

    This means that their metabolism is strongly dependant on their body’s temperature. Colder water will inevitably slow down 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 with 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 diagnose is not always possible.

Be prepared for everything.


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

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

Leave me a comment below if you need more answers.

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What about when none of these seem to be the case? I have an outdoor pond with goldfish and one has been upside down at times. Does not otherwise look or act ill, no obvious injury, and it’s not feeding time of year yet, so not constipation. He will look ok for a few days, then be upside down. Local pond store tested the water as normal and said it sounds like maybe a tumor or something?


Two of my goldfish lie moribund on their sides in my garden pond. When I try to net them, they become active and swim away, only to resume their positions. Any suggestions what might be the problem? Thank you.


Thank you so much for your very helpful article. My carp started floating sideways at the surface 3 days ago, I followed the recommendations, cleaned the pond, treated with antibiotic and fed peas. This morning he is right way up and swimming around but staying on the surface and not able to stay under. Obviously he has buoyancy issues still. He did not eat the peas today. What more should I do now?

Linda Esposito

My year old glow fish has been swimming upside down, round and round, right side up, nose up in circles for a long time now. He is very energetic, eats well. I have 7 other fish in the tank that are fine, 2 being his glow fish buddies.


Why is my fish floating upright in the surface even if it doesnt have bloated belly ?


My glo shark has been swimming upside down for several days now, however, at times he’ll act normally but then go by the filter and continue swimming upside down. I’ve had him and my two other glo fish for 10 months now, this is the first time he’s acted this way.. and I’m concerned its distressing my other two.


That’s the same with my fish..

Denise R Alarid

When we needed to remove are bala sharks cuz they got too big during The netting process I believe my Angelfish got injured now it’s swimming upside down trying to swim really hard it’s still eating I’m making sure of that I getting the food down to her I don’t know what to do I don’t know if she can survive this as from an injury and I heard you can get swim bladder from an injury do you know of any way I can treat this it’s been at least a week now I tried peas that did not… Read more »

Shannon Lindsey j

Hi my name is Shannon I have my buddy parrot fish he has been in a his tank now for 2 days I fed him peas with Epsom salt on them and.yes still up at the tank he is active wheniwhen I feed him he eats he sometimes swims to v9ttom buy comes right back up to top his belly looks to me a way better than before but I know it’s gonna be a long road be4 my little buddy makes revovery.i really dont know.what to do to make a homemade device that keeps him staying on bottom instead… Read more »

Shannon Lindsey j

Hi my fish has been swimming on the top sideways and sometimes goes to the bottom but comes back up he’s a parrot fish he’s my buddy I have put him in a hospital tank for past 2 days with pea diet and meds.but to me it looks like his belly was sweeled some we’ll a lot looks to me like it’s going down but idk can u plz help me

Mehak Imran

My goldfish is just laying sideways but only on the right side not left
It’s breathing and I have separated it from other fish as it has a head injury which other fish were eating
She won’t mkbe and is sitting in a corner I lut her a bit back and she just moved her tail and went back to the corner
What do I do will she survive