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Why Is My Goldfish Swimming Upside Down?

Lindsey Stanton Profile Picture

By Lindsey Stanton

goldfish swimming upside down

Ever found yourself asking the question, “Why is my goldfish swimming upside down?” If you look in your tank only to see this, it doesn’t necessarily mean they’re dead, so don’t flush them just yet!

In fact, it’s fairly common for goldfish to end up floating and swimming upside down, but that doesn’t mean it’s normal behavior. Buoyancy problems such as swimming sideways or upside down in their tank is a sure sign that there’s something up with your goldfish.

This article is going to shed some light on what’s happening and what you can do about it. There are few possible reasons, nearly all are down to poor health, but the good news is, it’s pretty much always curable, too.


Why is My Goldfish Swimming Upside Down? What is the Most Likely Reason?

Image By: M-Production, Shutterstock

If your goldfish is swimming upside down, the most probable cause is swim bladder disease or disorder. Despite the name, it really isn’t a disease; it’s a symptom of one of several issues that could be affecting your goldfish’s swim bladder.

The swim bladder is a gas-filled internal organ that fish use to regulate their buoyancy and move up and down normally in water.

So, when something’s affecting it, it can cause a fish to float upside down or on swimming on its side, which are unmissable symptoms of swim bladder disorder.

What Might Have Caused it to Happen?

Fancy goldfish are prone to issues with their swim bladders, especially those varieties that have been bred to have bulbous or balloon-like bodies, like most fancy varieties.

That said, there’s still always a reason behind SBD, so let’s look at some of the possible causes:

  • Constipation. Feeding a poor-quality diet or too large a meal can cause your goldfish to become constipated, and the blockage can temporarily stop the fish from being able to regulate their swim bladder.
  • Swallowing air. If you feed your goldfish flakes or other foods that float on the surface of the tank, they may ingest a large amount of air when they eat, which can cause issues with their swim bladder.
  • Food expanding in the stomach. Certain types of dry pellets and freeze-dried food expand when moist, so if your fish eats it as soon as it hits the tank, it can expand in their stomach, which stops them from being able to properly regular their swim bladder.
  • Bacterial infection. Sometimes SBD can be a symptom of an underlying bacterial infection.
  • Changes in water temperature. Certain varieties of goldfish—such as round-bodied varieties—are susceptible to sudden changes in water temperature.
  • Large amounts of nitrate in the water. Some fish keepers have found their goldfish react badly to having high levels of nitrate in their aquarium water.

Should I Be Worried About My Goldfish Floating Upside Down?

An upside down fancy goldfish isolated on a black background

Usually, swim bladder disorder is simply caused by eating too much food or ingesting air with the food, and should fix itself with a few days of fasting your fish.

However, if your fish also looks unwell (for instance, if it looks lethargic and has legions or discolored scales), it may be the sign of a bacterial infection. In which case, you should be more concerned and it may warrant a trip to the vet.

What Can I Do to Treat the Problem?

The treatment for swim bladder disease depends on the cause.

If the issue is down to water quality (like too high nitrates), then the cure can be simple! Make sure you improve on the water quality care for your fish tank. Start with a large water change, clean the substrate of any waste and uneaten food, and then make sure to perform ongoing monitoring of key factors using a water quality testing kit. Ensure all parameters are within safe levels.

If the problem is down to constipation, which is very common, the first thing you should do is to ‘fast’ your goldfish for 3 days. This means do not feed them at all for 3 days, to give their digestive system time to clean itself out completely.

Next, you should feed your goldfish cooked and shelled peas at a rate of about 2 to 3 per day, which is a known way to relieve constipation issues, then move them back onto a species-specific diet.

However, if the swim bladder disease is due to a bacterial infection, is a genetic defect or the swim bladder has some form of permanent injury, feeding peas will not have any effect; this is only for constipation-related issues.

If, after fasting and feeding peas, the issue persists, you can rule out digestive issues and then have to try cures for alternative causes.

Can Swim Bladder Disease be Cured?

Celestial Eye Goldfish
Image Credit: Dan Olsen, Shutterstock

Sometimes it can, yes. Though, sadly, it can be permanent.

Usually, it’s just an issue with the digestive system that affects the swim bladder. As suggested above, a few fasting days, followed by feeding skinned peas will alleviate the problem. However, if it’s due to permanent swim bladder damage, or genetic in nature, there may not be a cure.

Is Swim Bladder Disorder Fatal?

Unfortunately it can be, but some fish can live many years with the problem. It depends on the cause and the severity.

Mostly, if the issue is down to digestive issues or bacterial infection, it can be treated and will clear up. However, if the infection leaves lasting damage, or if the SBD is down to a genetic defect, it’s not curable and may be present for the rest of the fish’s life.

Even if permanent though, it’s not necessarily fatal. Most fish seem able to cope with it, can right themselves often enough to be able to feed and perform natural behaviors, so SBD isn’t fatal in itself.

Is There a Way to Prevent Swim Bladder Disease?

The best way to deal with swim bladder disorder is with a pre-emptive strike. Here are some ways you can lessen the chance of it ever developing.

  • Feed foods that sink to the bottom of the tank rather than floating on the top.
  • Avoid feeding dried pellets or freeze-dried foods unless you soak them before putting them into the tank.
  • Don’t overfeed your goldfish.
  • Make sure the water in your tank is kept at a stable temperature.
  • Check the water parameters in your tank to make sure it’s not too high in nitrates or any other undesirable substances.

If you're new to the world of goldfish or are an experienced goldfish keeper that loves to learn more, we recommend you check out our best-selling book, The Truth About Goldfish, on Amazon.

From diagnosing illnesses and providing correct treatments to ensuring your goldies are happy with their setup and your maintenance, this book brings our blog to life in color and will help you to be the best goldfishkeeper you can be. 



Most goldfish found swimming upside down are suffering from some form of SBD. On its own, it isn’t necessarily too serious, but it can be a sign of a more problematic underlying issue.

In many cases, swim bladder issues will go away on their own or can be dealt with at home. But, if in doubt, it’s wise to seek advice from a veterinarian who’s experienced in working with aquatic creatures.

Happy fish keeping!

Featured Image Credit: M-Production, Shutterstock

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