what causes swim bladder disease in angelfish?

Why Is My Angelfish Swimming Sideways?

Swim bladder disease in angelfish results in the fish swimming oddly or frantically. The disorder itself is a progressive illness that eventually renders the fish unable to swim properly. Unable to maintain buoyancy, it floats upside down or on its side. A bad swim bladder is usually a symptom of another illness, rather than a standalone disorder.

Swim bladder disease is caused by a wide variety of primary issues. Most can be prevented with proper feeding and care. The most common trigger is improper tank parameters that result in constipation. Over-feeding, which also results in constipation, can escalate to the point of being deadly. Providing a healthy tank and proper diet goes a long way to preventing this disorder.

Untreated swim bladder disorder will eventually lead to the fish being unable to breathe or eat properly. If the trigger of the disorder doesn’t kill the fish by itself, this will. There are treatments for swim bladder disorder, including feeding the fish cooked peas, correcting tank parameters, and medications. The treatment will depend on the affliction, and this isn’t always easy to identify.

What Causes Swim Bladder Disease In Angelfish?

Swim bladder disease, also called swim bladder disorder, is the name given to a broad collection of issues that affect the swim bladder. It results in the fish being unable to swim or orient itself properly.

All alone, swim bladder disease is usually a symptom of these issues, not actually a primary issue with the bladder itself. We can broadly group the causes of swim bladder disease into 4 categories. They are:

  • Incorrect tank conditions
  • Birth defects
  • Parasitic or bacterial infection
  • Over-feeding

Swim bladder issues in angelfish can be hard to deal with. First off, it’s distressing to witness your beautiful fish suffering. After that, it’s highly difficult to pinpoint the exact cause and bring it to a stop. Without knowing the trigger, resolving it will be a trial and error fiasco.

Even still, you must treat your fish. Failing to do so will result in an unhealthy fish with a low quality of life. Eventually, the angelfish will die.

Angelfish Swimming Weird

The first sign is usually your fish ‘swimming weird’. This is because a swim bladder that functions correctly will have your fish able to swim in clear, straight lines without wavering.

The swim bladder is an organ found in fish and is filled with a mixture of gas and air. As stated in Respiratory Physiology and Neurobiology, this organ enables fish to float at specific depths in the water without actively swimming. This helps to:

  • Conserve energy
  • Let the fish have moments of low activity or rest
  • Maintain camouflage; for example, predatory fish use this careful floating to blend in and then ambush prey

Certain fish are able to control their buoyancy by increasing or decreasing the amount of gas in the swim bladder. Other fish maintain a fixed amount that does not change unless forced to, like when they’re afflicted by swim bladder disease.  

The location of the swim bladder can change depending on fish species. However, it’s usually found in the cavity below the spine and above the belly. Not all fish have a swim bladder, and achieve desired buoyancy through other means. In angelfish, the swim bladder is near the center of the body, along the lateral line, and starting shortly behind the eye.

do fish suffer with swim bladder disease?

What Causes Swim Bladder Disease In Angelfish?

Understanding the causes of swim bladder disease can help you prevent certain triggers for the ailment. It can also help you diagnose existing issues with your angelfish.

Aquatic veterinarians can help you assess your individual tank and its unique issues. You can also reach out to local aquariums or pet shops. They have a wealth of experience with swim bladder disease, and can usually perform tests on any water samples you provide.

You can also try to diagnose the problem at home. Let’s explore the factors that might’ve caused the swim bladder issue to crop up in your tank.

Incorrect Tank Conditions

Poor tank conditions are the main cause of swim bladder disease. Your fish may have a range of ailments if they live in a tank with:

  • Dirty water
  • Water that’s too hot or cold
  • An incorrect pH balance
  • The wrong measure of nitrates

Individually, these factors may cause swim bladder issues in angelfish. Even though angelfish are considered a hardier fish, tolerant of a wide range of conditions, improper conditions will impact their quality of life.

For example, a too-cold tank will affect how effectively fish can digest and metabolize food. This can lead to impaction, which applies pressure to the swim bladder, and can lead to swim bladder disease.

Dirty water or water with an incorrect pH balance may also cause the fish to internalize bacteria or diseases. This can disrupt its immune system, damage its organs, and eventually hurt the swim bladder. The ideal tank conditions for angelfish are as follows:

Temperature Range78° F – 84° F
pH Range6.8 – 7.8
Hardness54 – 145 ppm

Birth Defects

Just like with any other living organism on earth, fish can grow defects early in life. Occasionally, these defects will be within the swim bladder itself. They may also be on neighboring tissues, organs, or skeletal structures. Such defects will apply pressure or damage to the swim bladder.

Goldfish, koi, and betta fish are known for developmental defects that cause swim bladder disorder. Angelfish are too, to a lesser extent. In a study on one species of angelfish, Pterophyllum scalare, Aquaculture found that multiple larvae from a single clutch had incorrectly developed swim bladders.

If your angelfish has a birth defect that impacts its ability to swim properly, it will typically die before reaching adulthood. If your angelfish is much older, it’s either very lucky or the condition has a different cause.

Parasitic or Bacterial Infection

Any parasite or bacterial infection that attacks the swim bladder can quickly trigger swim bladder disease. Parasites found in aquariums that cause such damage are typically rare, but not unheard of.

Injuries can cause the swim bladder to rupture, or open a wound ripe for infection – especially in tanks with poor water quality. Such injuries can come from the fish swimming into a hard or sharp object or fighting, as most cichlids are known for.

Issues with the surrounding organs can also press on the swim bladder, such as cyst formation or egg binding. There is little that can be done for such fish.


Over-feeding causes a number of problems in all types of fish, including angelfish. The same is true of feeding too much freeze-dried food (as it expands in water), or incorrect food. Angelfish are omnivores that require a diet composed of plant and animal matter. Only providing the fish with one can cause a nutritional deficiency, among other things.

A common result of improper diet and over-feeding is constipation. Swelling of the intestine can push on the swim bladder organ, causing problems. Over-feeding can result in a mild case of swim bladder disorder, resulting in difficulty swimming.

Usually, this fades within a few hours as the fish’s body digests the food. If your fish appears to struggle to swim after eating, then cut back on the amount it is fed.

What Does Swim Bladder Disease Look Like?

Swim bladder disease presents itself in a number of easily observed ways. The one that most people notice is when the fish begins swimming abnormally. That’s because swim bladder disease makes it difficult for fish to maintain equilibrium and move around the tank. This will appear as the fish struggling to remain upright.

  • It will swim on an angle
  • It will swim upside down
  • It will try to right itself, only to flip back over

Buoyancy issues will also manifest. This will show as the fish:

  • Sinks to the bottom of the tank, looking as if it is resting on the bottom
  • Floats at the surface, bobbing there on its side
  • The angelfish may also appear to swim frantically as it struggles against its lack of control

Swim bladder disease will also impact your angelfish’s appetite. It will:

  • Have no appetite
  • Be unable to eat properly
  • Have a bloated belly, curved back, or other unusual bulges in its abdomen.

Angelfish that are in critical condition may also appear lethargic. After all, it’s exhausting to fight against your own balance, or it may be dying, which will sap it of all energy.

Why Is My Fish Swimming Vertically Head Up?

Your diseased fish may also begin swimming straight up-and-down. Before the full disorder sets in, the swim bladder will only be partially damaged. It will do a half-good, half-bad job of keeping your fish upright, which may cause the fish to:

  • Float at an angle
  • Float with its tail higher than its nose
  • Float with its head up vertically

Issues with the swim bladder can cause a range of odd buoyancy issues. If you notice this, be sure to examine the fish closely. If you notice any it trying to swim frantically, or showing body defects, this will help confirm the sickness it has.

If you don’t notice any other symptoms, check your filter. Sometimes, a filter’s output is too hard, making it difficult for the fish to swim properly. Angelfish need a gentle current.

angelfish swim bladder treatment

Dropsy Or Swim Bladder Disease

It’s easy for new fish-keepers to misdiagnose their angelfish with dropsy. Both dropsy and swim bladder disease will cause your fish to float oddly or swim erratically. However, dropsy has clear symptoms that set it apart:

  • Your fish will have pine-coned scales that protrude from its body
  • It will heavily bloat and be unable to eat

Dropsy is rather easy to treat, although it’s fatal if you don’t address it quickly. It’s a kidney disease that will shut down your fish’s organs. If you notice the above symptoms, you can treat the fish with Epsom salt and a mild dose of kanaplex.

Can Fish Die From Swim Bladder Disease?

Is swim bladder disease fatal? It can be. If your fish is not properly treated, it will be deadly.

It is a symptom of a wide variety of issues. Your fish may be more or less likely to die, based on what that root disease is.

As noted by Midland Veterinary Surgery, there are several terminal illnesses that trigger swim bladder disease. Severe constipation or infection may be one of these issues. On its own, swim bladder disease will make it extremely difficult for the fish to:

  • Swim
  • Eat
  • Breathe

This alone may eventually cause it to die. If you suspect that your angelfish has swim bladder disease, get on top of it straight away.

How To Treat Swim Bladder Disease

Treatment for swim bladder disease will depend on what has caused the disorder to develop in the first place. If you can’t determine the cause yet, start with the basics:

Check The Tank

Check the parameters of your tank and set-up. You may find an imbalance in the water’s

  • Temperature
  • Hardness
  • Acidity

Should anything be unusual, perform a 20% water change and correct the parameters. You may also want to add aquarium salt to help the fish recover.

Quarantine The Fish

In most cases, it’s wise to put the fish in a separate quarantine tank. This makes treatment easier, and stops other fish from picking on the weak tank mate. Separating the afflicted fish from any others also makes the next treatment option much easier.

Change Filter And Temperature

Lower the filter output current to a gentler setting. This will keep your already weak fish from being pushed around the tank, which could:

  • Exhaust it
  • Cause it to bump into objects
  • Make it struggle to eat

Alongside this, you should adjust the temperature of your tank. As tropical fish, angels do best in warm water. A setting of 80° F will give your angelfish the comfort it needs to begin healing.

Treatment For Different Causes

Now it’s time to be more specific. These treatments apply to the different root causes of the disease.


If your tank conditions are otherwise fine, the most common reason for swim bladder disease is constipation or food impaction.

Change Diet

In this case, you should not feed the fish for 2-3 days. It may seem cruel, but this prevents additional food from blocking up the fish’s internal systems.

After this period, feed the fish a cooked and skinned pea. Just one! These fish are small, and yours is already dealing with a stomach issue. Peas are full of fiber and great for helping matter to shift through the stomach and intestines.

Repeat this once a day for an additional 2-3 days. If the fish shows signs of recovery, you can begin alternating between peas and normal fish food. It’s best to avoid:

  • Freeze-dried foods
  • Flakes
  • Floating pellets

These can hamper recovery. Instead, live brine shrimp or frozen-thawed brine shrimp are an excellent choice. Angelfish in this stage need protein.


If your fish is struggling to swim, it may also have difficulty eating. This will require you to hand-feed the fish. If the fish refuses to eat or this treatment is ineffective, then a different treatment is required.

It’s also possible that the angelfish’s disease has progressed too far. If it is dying, you should discuss euthanasia with a vet.


If the disease is the result of an infection, then you need to treat the entire aquarium. Anti-bacterial solutions can be added to the tank, which helps if a bacterial infection attacked the fish internally. You can find options at your local pet shop, or you can contact your vet to receive stronger medications.

You can also add a small amount of aquarium salt to the tank. This will ensure the angelfish are hydrated and full of electrolytes.


If your fish has a birth defect, this will require the intervention of a vet. A professional can perform corrective surgery on the fish. In some cases, this:

  • Repairs any damage to the organ
  • Removes liquids from the bladder
  • Relieves excess gas from the bladder

A vet may also surgically attach a floating harness to the fish if its swim bladder has trouble inflating. This allows it to remain upright and closer to the surface, so the bladder can return to normal and inflate.

Vets can also prescribe antibiotics unavailable as over-the-counter purchases. These will be a more targeted medication, rather than a broad-spectrum solution.

how long does swim bladder treatment take to work?

Can Swim Bladder Disease Go Away On Its Own?

Swim bladder disease will only resolve itself in one scenario: if it’s triggered by light constipation. Even without your intervention or any dietary changes, the angelfish may recover from constipation. The swim bladder issues will then resolve themselves.

However, in most cases, angelfish do not recover from swim bladder disease on their own. It will take some form of intervention and treatment on your part. The condition will continue to worsen until the fish is unable to swim or breathe properly.

Is Swim Bladder Disease Contagious?

Thankfully, those with community tanks need not worry about a contagious outbreak. Swim bladder disease is not contagious to other fish.

With that said, depending on what has caused one fish to develop this disease, others may soon follow. That’s why diagnosing and resolving the problem is critical. As an example, poor water quality or a chemical imbalance will lead to multiple problems with your fish.

Do Fish Suffer With Swim Bladder Disease?

No one wants their pets to suffer. Sadly, a fish with swim bladder disease that isn’t responding to treatment isn’t going to get better.

Even if your vet attached a floating harness in the hopes of aiding the fish in its recovery, this is only a temporary fix. Anywhere the harness makes contact with the angelfish’s skin will eventually grow sores and infection. The harness will rub away the slime coat and skin.

As you may fear, this isn’t good for the fish’s quality of life. If swim bladder disease cannot be stopped and reversed with treatment, then it’s time to speak to your vet about humane euthanasia.

A recovered angelfish with a permanently damaged or defective swim bladder may live a full life. That’s only true if it’s still able to swim mostly upright. You will have to accommodate its inability to swim by using a gentle filter output and hand-feeding it.

Preventing Swim Bladder Disease

Preventing swim bladder disease is rather simple, all told. Since the most popular cause is improper tank parameters, let’s begin there.

Check Water Parameters

Angelfish are hardy, but thrive in properly heated water with a gentle filter output. Ensure that your tank is set to the parameters noted earlier.

Check Filtration

Are you only using mechanical filter media? If possible, swap part of it out for a biochemical filter media that removes nitrates and ammonia from the water. This improves the water quality and removes impurities, stopping harmful bacteria populations from exploding.

Avoid Keeping Too Many Fish

Over-crowded tanks are susceptible to the above problems. Be sure to not over-populate your tank.

Check Diet

Next is the diet. Include variations in the food you feed the fish, rotating between:

  • Frozen foods
  • Granules
  • Pellets
  • Flakes

This will ensure your fish’s nutritional needs are being met.

Avoid Over-Feeding

Only provide an amount of food that can be eaten within 2-3 minutes. That’s especially true for dried foods, like flakes and pellets. These foods continue to expand in the angelfish’s stomach, causing constipation and impaction. It helps to soak any dried foods in water prior to feeding them to the fish.

Clean Your Tank

Be sure to perform regular tank maintenance. This will keep the water clean and the tank healthy.

Swim bladder disease is an affliction that is common in aquarium fish of all types. Angelfish are no different. As long as you keep your tank conditions healthy, and watch for signs of infection, your angelfish will be less likely to develop it in the future.