7 Reasons Your Fish Is Swimming Sideways (& What To Do)

Last Updated on 2024-05-11

You check your fish tank and notice that one of your fish appears to be swimming sideways. You may think that it’s sleeping or it’s going to die. Your fish isn’t going to die, but it sure isn’t doing very well.

Your finned friend most likely has a disease called swim bladder disease, which is caused by a lot of factors. It could also be a sign that your fish has a much more serious illness.

It can be mild or severe, and some may even lead to death. Read on to learn more about why your fish is swimming sideways.

Why Is Your Fish Swimming Sideways?

If your fish swims on its side or upside down, it might have swim bladder disease. This means that your fish is having trouble controlling its swim bladder, an internal organ that helps the fish control its buoyancy or stay at a certain depth without having to swim. It also makes sure the fish stays upright. 

Swim bladder disease is a common illness in aquarium fish that makes the fish swim upside down or sideways because their bladder doesn’t work right. People often call it a “disease,” but it’s actually a symptom that can be caused by things like constipation, sudden changes in temperature, bacteria, or parasites. When these things happen, the organs inside the fish can push up against the swim bladder making your fish swim in an unusual pattern.

Luckily, swim bladder disease is usually easy to fix as long as you notice them early. It can be temporary or last for a long time, depending on what caused them. Even if your fish has permanent swim bladder damage, they can still have a happy life.

What To Do If Your Fish Is Swimming Sideways

Swim bladder disease, which is also called fish buoyancy disorder, is a complicated condition. There are various things that could have caused it, and if you treat it wrong, it could get worse. Make sure you know exactly what caused it before you try to treat it. So, here are a few things you can do to help your fish swim back up the right way.

1. Food Fasting

If you think that a swim bladder disorder is caused by a bloated stomach or intestine that is too big, you should stop feeding the fish for three days. This will give the fish some time to digest the food that got stuck in its stomach, relieving pressure against its swim bladder and stopping it from swimming sideways.

2. Adjust The Water Temperature

Be careful when changing the water’s temperature in your aquarium because it can throw off the balance of the whole thing.

You can put your sick fish in a separate aquarium and keep the water in that aquarium between 78 and 80°F. This will help keep their metabolism in check and can keep them from swimming sideways.

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3. Give the Fish Peas

Peas have been widely recognized as a treatment for swim bladder disease, and most aquarists will advise you to give them to your fish if they begin swimming sideways. To prepare this, you can boil or microwave peas, then peel off the skin when it’s done. But the fish can’t get many of the nutrients they need, so this shouldn’t be a regular part of your diet.

4. Administer Antibiotics

A swim bladder disease can also be caused by an infection. The fish may have an inflamed swim bladder, which makes it hard for it to stay upright and makes it swim sideways.

This can be treated with antibiotics, but unfortunately, it’s not recommended that you do it on your own. You can ask a local vet for help giving antibiotics to the fish in your aquarium.

5. Stabilize Water Quality

The environment that fish live in is also a common cause of swim bladder disease. When the water quality is bad, fish may feel tired and stressed, which can make them unable to use their swim bladder properly, and which makes them swim sideways.

Make sure to keep the tank water in pristine condition by changing the water in the tank often, keeping an eye on the ammonia or nitrate levels, and keeping the temperature stable.

The best way to keep the water quality in the tank perfect at all times is to also use a filter. You should pick a filter that turns over 3-4 times the amount of water in the tank per hour.

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A male guppy (Poecilia reticulata), a popular freshwater aquarium fish Ein männlicher Guppy, (Poecilia reticulata) ein beliebter Süßwasser-Aquarienfisch

What Is Swim Bladder Disease?

If you find your fish swimming funny or acting strange, it might be showing symptoms of swim bladder disease. It is an illness that makes a fish unable to control its swim bladder. This can make your fish swim on top of the water in the aquarium, sink to the bottom, swim sideways, or even float belly-up on their backs.

Swim bladder disease can make your fish’s spine look bendy, and the area around the stomach will look bloated. Your fish will have trouble swimming and eating as a result. This may transpire for a number of reasons, like living environment, feeding behavior, bacteria, and parasites, and it is a certain sign that your fish is stressed.

Swim bladder disease is not contagious because it is not a disease. It’s more likely a symptom of another illness your fish is suffering from. But because they all live in the same conditions in an aquarium, all of your fish are at risk of getting sick. If the illness is not treated quickly, it can be fatal.

What Causes Swim Bladder Disease?

When a fish is experiencing swim bladder disease, it means that the fish is stressed and uncomfortable. This illness can be caused by a variety of things, including physical problems, the environment, and what they eat. If you find that your fish is swimming sideways, it could be because of one of the following:

1. Improper Feeding

Improper way of feeding can be a big cause of swim bladder disease. These include things like overfeeding, feeding with freeze-dried food or dry flakes that expand, and taking in too much air from floating foods. This can cause your fish’s belly to get bigger, which can put pressure on the swim bladder.

2. Shock

Fish can also get swim bladder disease if their environment changes suddenly. There is no effective treatment for this yet when this happens, but the fish will likely recover within a few hours. Shutting off the lights removes one stressor and encourages the fish to rest rather than swim around, which can be helpful.

3. Deformity of An Internal Organ

Swim bladder disease can also occur when the organs in the fish’s abdomen get bigger. For example, the liver and kidneys can get cysts or growths, which puts pressure on the swim bladder, making it harder to control.

4. Water Quality

Poor water quality can surely put your fish under stress. When the water quality is bad, fish can experience sudden and ongoing stress, which upsets the normal balance of homeostasis, which can lead to swim bladder disease. You can keep your tank clean by vacuuming the gravel, changing some of the water every week, and checking the water’s temperature, pH, and hardness every once in a while.

5. Bacterial Infection

People often wrongly assume that a swim bladder infection is a standalone disease, but in most cases, it is only one part of an infection that has spread throughout the fish. Usually, the fish would show signs of bacterial infection before showing signs of swim bladder disease. When fish begin to exhibit symptoms of swim bladder disease, it’s probably very sick, making treatment extremely challenging.

6. Parasites

There are many kinds of parasitic worms that can infect aquarium fish, but they usually don’t cause any big problems. But if there are a lot of worms in the fish’s digestive system, it will cause problems in its swim bladder, making it hard for the fish to swim well. Luckily, there are medicines on the market that can help get rid of the parasites living inside a fish.

7. Physical Damage

When fish fight over territory, they sometimes hurt their swim bladders in the process. The best way to help sick or hurt fish get better faster is to put them in a special quarantine tank that is big enough to keep them from getting any worse. To avoid this from occurring, you should be careful when choosing tankmates for your fish to reduce the chance of fighting.

Fish Twitching and Swimming Sideways

If your fish is twitching and swimming in a strange way, it could be experiencing shimmy. When a fish shimmies, it waves its body from side to side. This is usually followed by other strange actions and behaviors, like clamping its fins, shaking its head in an odd way, swimming sideways, and heavy breathing.

Shimmying is not a single disease, but rather a sign that a fish’s nerves and muscles are no longer working properly, causing the fish to twitch. It happens when fish are under a bunch of stress, most of the time because of problems in their environment. Also, it can happen with other symptoms, especially those related to stress, poisoning, and problems with the chemistry of the water, such as making too much slime, having cloudy eyes, feeling full, and being tired.

Some fish may shiver, twitch or shake their bodies when trying to assert themselves or trying to reproduce, but no fish will do this all the time. So, you can quickly tell if your fish is doing the shimmying behavior.

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Why Is Fish Bloated and Swimming Sideways

Your fish probably has swim bladder disease if it swims all over the place and has a bloated belly. This disease is pretty common in fish tanks, but it usually means there is a much bigger problem. Continue reading to find out why your fish is bloated and swimming sideways.

1. Overeating

When a fish eats too much, it causes its stomach to get bloated. To fix this, you might stop feeding your fish for at least 24 to 48 hours to give it time to recover from digestion problems. Make sure you pay attention to your fish’s feeding pattern to prevent overfeeding.

2. Excessive Gas

If you provide your fish with too much food that floats on the water’s surface, it will take in more air as it eats. Taking in too much air causes problems with the swim bladder, making it bigger and bloated. To prevent this from happening, you can soak food for a few seconds in the tank water making sure it will sink before putting it in the tank. 

3. Bacterial Infections

When bacteria makes a fish bloated and causes it to swim sideways, this is usually a sign that the fish needs help right away. Antibiotics are usually used to treat bacterial infections in a fish’s swim bladder. It is strongly suggested that you talk to a vet before treating this.

4. Parasites

There are a lot of parasites that find fish guts to be an ideal home. For example, callamanus worms feed by attaching themselves to a fish’s digestive system, which causes the fish to bloat and swim sideways. Most of the time, it’s hard to find these parasites in their early stages, which makes them hard to treat.

5. Constipation

If your fish can’t get rid of waste, it will build up in its stomach and cause it to become bloated. So much so that the pressure affects the fish’s swim bladder, which makes the fish swim sideways because it can’t properly control its swim bladder.

Can You Cure Swim Bladder Disease?

If swim bladder disease is caught early, it can be cured. Most of the time, options on how to treat this disease depends on what is causing it. If you know for sure that your fish is sick because of a digestive problem, here’s one way to cure it.

First, you need to stop feeding your fish for at least three to four days. When your fish goes without food for a while, any problems with its metabolism can be cured. Then, on the fourth or fifth day, microwave or cook some peas and give them to your fish, as this will help them pass their stools and clean out their bodies, relieving them of constipation. Lastly, keep the water temperature in the aquarium to about between 78 and 80°F to keep their metabolism in check.

While your fish are getting better, it is a good idea to lower the water level in their tank a little bit. This will help the fish find food easier when they swim. Also, the filter can make cleaning any extra gunk quicker and easier.

Preventive Care and Tank Maintenance Tips

Keeping your aquarium fish healthy starts with proactive care and consistent tank maintenance. By establishing a routine that promotes a clean and stress-free environment, you can significantly reduce the likelihood of swim bladder disease and other health issues. Here are essential tips every aquarium owner should follow:

Regular Water Changes: Regularly changing the water in your tank is crucial for removing waste, uneaten food, and potential toxins. Aim to change 25-30% of the tank water every two weeks, adjusting frequency and volume based on tank size and fish load.

Proper Feeding Practices: Overfeeding is a common problem that can lead to digestive and buoyancy issues in fish. Feed small amounts once or twice a day, providing only as much food as your fish can consume in a couple of minutes. Opt for high-quality, species-appropriate food to ensure nutritional balance.

Monitor Water Quality Regularly: Use water testing kits to regularly check parameters such as pH, ammonia, nitrite, and nitrate levels. Keeping these within safe ranges is essential for the health of your fish. Adjustments should be made promptly if any parameters deviate from recommended levels.

Aquarium Placement and Setup: Ensure your tank is placed in a stable, low-traffic area to minimize stress from external disturbances. Avoid direct sunlight, which can cause temperature fluctuations and promote algae growth.

Tank Equipment Check: Regularly inspect and maintain aquarium equipment, including filters, heaters, and air pumps. Ensuring these devices are functioning correctly helps maintain the environmental stability necessary for the health of your fish.

Aquascaping and Tank Enrichment: Create an enriching and naturalistic environment for your fish. This includes providing adequate hiding spots and territory markers, which can help reduce stress among fish. Live plants can also improve water quality and provide a more natural habitat.

How Do You Prevent Your Fish from Swimming Sideways

If you’ve finished treating your fish from swim bladder disease, you’d probably want to prevent it from happening again. Here are some tips you can do to prevent your fish from swimming sideways.

1. Occasionally Feed Green Peas

Green peas have a lot of fiber, which will keep the fish from getting constipated. They are often used to treat fish that swim sideways. You can boil green peas in a pot for a few minutes, then make sure to remove the skin before giving it to your fish.

2. Frequent Water Change

Infections and intestinal parasites that make the fish swim sideways are mostly caused by dirty tanks, which is why it’s so important to keep your tank clean. Make sure to change your aquarium water for at least 25% per week to prevent it from becoming toxic. Remove any extra food or trash you see in the tank to give your filter a break and make it last longer.

3. Give Proper Food

If you only have dry food to give your fish, wet it first to prevent it from floating. Don’t give your fish feeds that float so they don’t gulp down too much air, which can make them bloated. Usually, a bloated swim bladder caused by gulping too much air can cause your fish to swim sideways.

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4. Avoid Overfeeding

Make sure you feed your fish the right amount of food to prevent having problems with their stomachs. If you feed your fish too much, it can get bloated and constipated, which makes it swim sideways. As a general rule, you should only feed your fish what it can eat in two to three minutes.

5. Avoid Stressing Your Fish

When your fish swim sideways, it may be because they are too stressed. There are plenty of things that can stress out a fish. To prevent this from happening, don’t put your fish in a tank with too many other fish, and don’t put them in a tank with fish that like to fight. Also, don’t touch your fish, because that wouldn’t be good for them.

6. Give Your Fish A Safe Place To Swim

Sometimes, fish problems are caused by what we put in our aquariums. Fish are naturally curious, so they swim everywhere. Make sure that you prevent your fish from getting scratched by sharp edges on aquarium decorations or driftwood, which can tear off a fish’s fin and cause it to swim sideways.

Common Signs of Stress in Aquarium Fish

Understanding and identifying signs of stress in aquarium fish can be crucial in preventing health issues that may lead to symptoms like sideways swimming. Stress in fish can be caused by a variety of factors, including poor water conditions, inappropriate tank mates, or inadequate diet. Here are some key signs of stress to watch for in your aquatic pets:

1. Erratic Swimming: If you notice your fish swimming erratically or darting around the tank without apparent reason, this could be a sign of stress or discomfort within the tank environment.

2. Hiding or Withdrawal: While some fish are naturally shy, excessive hiding or a sudden change in a fish’s willingness to interact or feed can indicate that it feels threatened or stressed.

3. Changes in Appearance: Watch for changes such as faded colors, clamped fins, or spots appearing on the body. These can all be indicators of stress or illness in fish.

4. Rapid Gill Movement: Gills that move more rapidly than normal can be a sign that the fish is struggling to breathe, often due to poor water quality or a lack of oxygen.

5. Loss of Appetite: A sudden disinterest in food is a common symptom of stress or sickness in aquarium fish.

6. Aggression or Bullying: Changes in social behavior, such as increased aggression or bullying, can be a response to stress, often caused by overcrowding or incompatible tank mates.

By keeping an eye out for these signs, you can take early action to adjust the environment or care routine to reduce stress and prevent further health issues. Regular observation and quick response to signs of stress can greatly enhance the well-being of your aquatic pets.


Why Is Your Tetra Fish Swimming Sideways?

According to Pet Fish Online, tetras tend to swim sideways because they have a problem with their swim bladders. This makes the fish less buoyant, making it harder for tetras to swim normally, and they might even sink to the bottom. This is mostly because the water quality isn’t good enough.

Why Is Your Angelfish Swimming Sideways?

Angelfish with swim bladder disease will usually swim sideways, says Just Fish Keeping. The disorder is a disease that gets worse over time and makes the fish unable to swim properly. Most of the time, a bad swim bladder is a sign of another illness rather than a separate disorder.

Why Is Your Molly Fish Swimming Sideways?

Molly fish that swim sideways are caused by other organs pressing on the swim bladder and making it stop working. Buoyancy issues can also be caused by internal organ diseases and even eggs that are stuck together.

Why Are Your Glofish Swimming Sideways

Most of the time, glofish swim sideways because they have swim bladder disease. A swim bladder is an organ inside bony fish that is filled with gas and helps them stay afloat. And if the fish’s bladder is affected by illness, injury, or anything else that isn’t normal, it will be hard for the fish to stay afloat, so it will swim in strange ways, like sideways.

Why Is Your Goldfish Swimming Sideways

Swim bladder disease or disorder is almost always the cause of a goldfish swimming sideways. Even though this word is often used to describe diseases in fish, it is actually a sign of a bigger problem.


Swim bladder disease, which affects a lot of aquarium fish, can cause fish to swim in strange ways. It can be caused by many things, like the quality of the water, temperature, or the way the fish eat. There are a lot of ways to treat and even stop it, which is good news. You can learn more about swim bladder disease and how to deal with it by reading the article above. If you do these things, your fish will be safe and healthy.

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