Here’s Why Your Goldfish is Swimming Sideways

Although smaller than other pets, goldfish are still an important part of our family. When one of our goldfish gets sick or starts swimming sideways, it is important to know why it is happening and how to treat it.

The most common reason a fish will swim sideways is called Swim Bladder Disease. A healthy swim bladder is necessary for a goldfish’s survival. Swim Bladder Disease can be life-threatening and must be immediately treated. It can be cured by a change in diet or changing the tank’s water. 

The swim bladder is one of the most important parts of a goldfish’s body and is also one of the most sensitive. Keep reading to learn what’s causing your goldfish to swim sideways as well as how to treat it.

Causes for Sideways Swimming

If your goldfish is swimming sideways, it can be quite alarming. And the truth of the matter is, it should be. Sideways swimming or laying upside down is a sign of a life-threatening illness.

When a goldfish swims sideways it is almost always diagnosed as Swim Bladder Disease or Disorder. Although this term is widely used for describing fish illnesses, it is actually a symptom of an underlying illness.

For example, if your goldfish is swimming upside down it may be that constipation has strained the swim bladder. Rather than curing the Swim Bladder Disease, you should instead focus on treating constipation.

Constipation is a common cause of swim bladder disease; however, there are many other illnesses that can lead to the disorder.

Other causes for sideways swimming include:

  • Improper Feeding
  • Bacterial Infection
  • Water Temperature Change
  • Dirty Water

Each of these issues varies greatly yet somehow all can affect your goldfish’s swim bladder. Keep reading to learn more about your fish’s swim bladder and how to treat each of the illnesses listed above.

What is a Swim Bladder?

Nearly every fish species has a swim bladder. The swim bladder is typically located at the bottom of the fish behind the front fins.

A swim bladder is appropriately referred to as the “air bladder” as it is filled with air in most fish. Some species have oil in their swim bladders instead of air.

Branching off of the digestive tract, fish use the swim bladder to help locate how far below the surface they sit. For example, if the barometric pressure changes, the pressure on a fish’s swim bladder will change too. The greater the barometric pressure, the higher in the water a fish will sit in order to alleviate its discomfort, and vice versa.

For fish in the wild, changes that affect their swim bladders can be remedied by simply swimming deeper or shallower into the water. Or even by changing locations entirely.

However, because aquarium fish do not have the ability to drastically change their location or depth in the water their swim bladders can be easily irritated. If this happens, it is up to you to remedy the problem.

Diagnosing and Treating Swim Bladder Disease


Swim bladder disease can be easily identified by either sideways swimming or a bulge near the fish’s stomach.

As aforementioned, swim bladder disease is often the result of another problem. Diagnosing the cause of your goldfish’s sideways swimming may be a bit more difficult because of this.

Think back on the past two days or so. Has anything changed in your goldfish’s care recently? Perhaps you tried feeding them a new food or accidentally overfed them. Maybe the tank is overdue for a water change or their water temperature changed drastically.

If something out of the ordinary took place in the last few days, it is likely the cause for your goldfish’s swimming sideways.

To help diagnose what is causing your goldfish’s swim bladder disease we’ll take a closer look at each of the main causes for this disorder.


Diagnosing constipation in fish may sound difficult, but if you know what to look for it is rather easy. Look around your goldfish’s aquarium for any poop. This will likely gather on the bottom of the tank if it has not already been sucked into the filter.

If you see nothing there, look towards the back of your goldfish. If they are constipated, you may be able to see the food mass gathering.


In the event of constipation, remove all food from your fish tank and abstain from feeding them until all symptoms have subsided.

If the fish is severely constipated, you may consider purchasing some fish laxatives to help move the food along. Literal laxative for fish is hard to come by and usually has to be specially ordered; however, for an at-home remedy, cut a frozen pee into small pieces and feed that to your fish. This will gently relieve the fish allowing the swim bladder to heal.


Improper Feeding

Everyone feeds their goldfish differently, but what most don’t realize is that some foods are more dangerous than others.

The most common fish food is typically a flake variety. Although cheap and easy to feed, these flaky foods force the fish to eat from the surface. This means they will have to swallow air to get the food, throwing off their swim bladder.

Other food issues are related to food expansion. If your fish food expands with water, it could expand in the goldfish’s stomach leading to constipation and swim bladder irritation.


Stop feeding your goldfish flaky foods if you notice they are swallowing too much air. Instead, opt for food that sinks slightly below the surface.

As for food expansion, you can either feed your fish less or pre-soak the pellets for more gentle digestion.

Water Temperature Change

Some goldfish are more susceptible to water temperature changes than others. If nothing has changed in your goldfish’s routine, check to see if the water is warmer or cooler than normal. Some filters can also help regulate tank temperature for easy care.


Keep the water temperature in your tank consistent. If there was a sudden change in temperature, gradually return it to the normal temperature.

Dirty Water

Aquarium fish are extremely sensitive to their water quality. If a tank has build-up on the wall and old food floating on the surface or sunk at the bottom, it is well past time for a change.

Goldfish are especially sensitive to a number of things such as nitrate in their water, use a water quality testing kit to ensure your fish has clean water to live in.


If your fish has swim bladder disease from dirty water, clean the tank immediately. Do not wait until the next day or until after work. Having clean water for a fish is like having clean air for a human, it is an absolute necessity!

After cleaning the tank, fill it with water and a water conditioner. Let the tank sit until it has reached the correct temperature and then return the fish. Monitor them for the next few hours to see if they remain on their side.

If the fish still acts sick awhile after cleaning, they may have contracted a bacterial infection and should take some antibiotics.

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Rick Kesler

I'm Rick and I've kept freshwater fish for over 5 years now. My main tank now is a 55-gallon tropical freshwater tank and my wife and I both just love watching all of our different fish while they swim around, some schooling and others not. I've also learned a lot about what to do and what not to do to keep our fish healthy and happy.

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