Swim Bladder Disorder in Fish

Swim bladder disorder can cause a fish to float, sink, swim sideways, turn upside down, or struggle to remain balanced. It is a symptom of an underlying problem rather than one specific disease.

Possible causes include poor water quality, dietary problems, infection, injury, abnormal organ growth, tumors, deformities, and damage to the swim bladder.

Begin by testing the aquarium water and observing the fish for swelling, sores, appetite loss, rapid breathing, or other symptoms. Treatment depends on the actual cause of the buoyancy problem.

Swim Bladder Disorder at a Glance

Common names: Swim bladder disorder, buoyancy disorder or floating disorder
Type: Symptom affecting buoyancy and balance
Affected fish: Many bony fish species
Common symptoms: Floating, sinking, tilting or swimming upside down
Possible causes: Water quality, diet, injury, infection, deformity or internal disease
Contagious: No, but an underlying infection may affect other fish
Treatment: Correct the underlying cause and provide supportive care
Prevention: Clean water, proper feeding, stable temperature and injury prevention
Prognosis: Depends on the cause

What Is the Swim Bladder?

The swim bladder is an internal gas-filled organ that helps many fish control buoyancy.

It allows a fish to remain at a particular depth without constantly swimming. Some fish also use the organ for sound production or hearing.

Different fish regulate their swim bladders in different ways. Some species have a connection between the digestive tract and swim bladder, while others regulate gas through specialized tissues and the bloodstream.

Not every fish has the same swim bladder structure. Treatment advice that helps one species may not be appropriate for another.

What Is Swim Bladder Disorder?

Swim bladder disorder is a general description for abnormal buoyancy.

The fish may:

• Float uncontrollably
• Sink to the bottom
• Tilt to one side
• Swim upside down
• Remain head-up or head-down
• Struggle to maintain position
• Roll while swimming

The swim bladder itself may be affected, but other internal problems can also press against it or interfere with normal swimming.

Symptoms of a Buoyancy Problem

Possible symptoms include:

• Floating at the surface
• Inability to swim downward
• Sinking to the bottom
• Inability to rise
• Swimming sideways
• Swimming upside down
• Tilting
• Rolling
• Head standing
• Tail standing
• Swollen abdomen
• Curved spine
• Loss of appetite
• Scrapes from contact with the substrate
• Red skin exposed above the water
• Labored swimming
• Exhaustion

A fish lying on the bottom may also be suffering from poor water quality, low oxygen, temperature shock, infection, or another serious illness.

What Causes Swim Bladder Disorder?

Possible causes include:

• Poor water quality
• Ammonia or nitrite exposure
• Overfeeding
• Swallowing air while feeding
• Constipation or digestive problems
• Infection
• Internal parasites
• Tumors
• Cysts
• Organ enlargement
• Egg retention
• Physical injury
• Spinal deformity
• Congenital body shape
• Gas supersaturation
• Sudden pressure change
• Incorrect temperature
• Neurological disease

Because there are many causes, no single treatment works for every fish.

Test the Aquarium Water First

Test:

• Ammonia
• Nitrite
• Nitrate
• Temperature
• pH

In an established aquarium:

• Ammonia should be zero.
• Nitrite should be zero.
• Nitrate should be controlled through appropriate maintenance.

Ammonia, nitrite, incorrect temperature, and sudden pH changes can cause weakness or abnormal swimming that resembles a swim bladder problem.

If ammonia or nitrite is present, perform an appropriate partial water change with conditioned, temperature-matched water.

Continue testing while the fish is recovering.

Observe the Fish Carefully

Before treating, determine:

• Does the fish float or sink?
• Can it remain upright?
• Is the abdomen swollen?
• Are the scales raised?
• Is the fish still eating?
• Is it passing waste?
• Are there red areas or sores?
• Is it breathing rapidly?
• Did the problem begin suddenly?
• Is more than one fish affected?

Take a short video. Abnormal swimming is often easier to evaluate on video than in a still photograph.

Swim Bladder Disorder in Fancy Goldfish

Fancy goldfish are particularly prone to buoyancy problems because selective breeding has produced rounded bodies and compressed internal anatomy.

Their internal organs and swim bladder may not be positioned as they are in longer-bodied fish.

Possible contributing factors include:

• Body shape
• Swallowing air
• Floating food
• Digestive problems
• Organ displacement
• Spinal deformity
• Long-term structural changes

Some fancy goldfish develop permanent buoyancy problems that can be managed but not completely cured.

Should You Isolate the Fish?

A hospital tank may be helpful when:

• Tank mates are attacking the fish.
• The fish needs medication.
• The fish cannot compete for food.
• Water depth needs to be adjusted.
• The fish requires close observation.
• Only one fish is affected.

A hospital tank should contain:

• Stable temperature
• Appropriate filtration
• Air stone
• Bare bottom
• Smooth hiding place
• Secure cover
• Frequent water testing

An uncycled container can quickly develop ammonia. Use an established sponge filter when possible.

How to Treat Swim Bladder Disorder

1. Test the Water

Correct ammonia, nitrite, unsuitable temperature, and unstable pH.

2. Stop Overfeeding

Do not continue adding food when the fish has a swollen abdomen or is unable to eat normally.

3. Observe the Abdomen and Waste

Check for swelling, raised scales, white waste, and difficulty passing waste.

4. Check the Food

Determine whether the fish gulps air while eating floating flakes or pellets.

5. Protect the Fish

Use a hospital tank or separate aggressive tank mates when necessary.

6. Adjust the Environment

A shallower water level and gentle current may help a weak fish reach food and the surface.

7. Choose Treatment Based on the Cause

Do not use antibiotics, antiparasitic medicine, or salt without a reasonable diagnosis.

8. Seek Veterinary Help When Necessary

Persistent buoyancy problems may require X-rays or other examination.

Should You Fast the Fish?

A brief fasting period may help when recent overfeeding or digestive fullness is suspected.

For an otherwise stable adult fish, withholding food for approximately 24 hours is often reasonable. The appropriate time depends on the species, age, health, and severity of the problem.

Do not fast:

• Very young fish for an extended period
• Severely underweight fish
• Fish with prolonged appetite loss
• Fish without considering their species-specific needs

Fasting will not cure tumors, infection, organ failure, injury, or a deformed swim bladder.

Should You Feed Peas?

Cooked, shelled peas are often recommended for swollen goldfish, but they are not a universal treatment.

Peas may provide fiber for some omnivorous or plant-eating fish. They may be inappropriate for fish that do not normally consume plant material.

Peas do not repair:

• A damaged swim bladder
• A tumor
• A bacterial infection
• Organ failure
• A spinal deformity
• Gas bubble disease

Choose food based on the fish’s natural diet rather than giving peas to every species.

Try Sinking Food When Appropriate

Some fish swallow excessive air while eating at the surface.

A sinking or neutrally buoyant food may help species prone to surface gulping.

Feed small portions and remove leftovers. Do not soak food unless the manufacturer recommends it, because prolonged soaking can cause nutrients to leach into the water.

Observe whether changing the feeding method improves the problem.

Treatment for a Suspected Infection

An infection may be suspected when buoyancy problems occur with:

• Redness
• Open sores
• Swelling
• Appetite loss
• White waste
• Rapid breathing
• Lethargy
• Several sick fish

Use medication only when it is appropriate for the suspected disease.

Antibiotics should ideally be selected with veterinary help. They will not correct every buoyancy problem and may harm the biological filter.

Do not mix medications or use leftover human antibiotics.

Swim Bladder Problems Caused by Injury

A fish may damage its swim bladder or spine after:

• Jumping
• Being dropped
• Rough netting
• Fighting
• Striking decorations
• Becoming trapped
• Sudden pressure changes

Place the fish in a quiet hospital tank with smooth surroundings and gentle flow.

Some injuries heal with time, while severe damage may be permanent.

Adjusting the Water Depth

A shallower hospital tank may help a fish that struggles to reach the surface or food.

Make sure:

• The heater remains safely submerged.
• The filter works at the lower water level.
• Water quality remains stable.
• The fish cannot jump.
• The fish can turn around comfortably.
• The water is deep enough for normal gill function and movement.

Do not lower the main aquarium’s water level if doing so will interfere with filtration or harm other fish.

Protecting a Fish That Floats

A fish trapped at the surface may develop redness, dryness, or sores where part of its body remains exposed.

Provide:

• Clean water
• Gentle flow
• Protection from strong light
• Easy access to food
• Smooth surroundings
• Appropriate water depth

Do not tape weights or objects to the fish. Specialized buoyancy devices should only be used with guidance from an aquatic veterinarian.

Protecting a Fish That Sinks

A fish resting on the bottom may develop pressure sores.

Use a smooth, bare-bottom hospital tank or another surface that will not scrape the fish.

Keep food within easy reach and maintain strong water quality.

Watch for red areas where the body contacts the bottom.

Can Epsom Salt Help?

Epsom salt, or magnesium sulfate, is sometimes used when constipation or swelling is suspected.

It is not a cure for all swim bladder problems, and an incorrect concentration may stress the fish.

Epsom salt is different from aquarium salt.

Before using it:

• Confirm species safety.
• Follow reliable instructions.
• Measure the water volume.
• Measure the dose accurately.
• Prefer a separate treatment container.
• Monitor the fish closely.

How Veterinarians Diagnose Buoyancy Problems

An aquatic veterinarian may use:

• Water testing
• Physical examination
• Swimming observation
• X-rays
• Ultrasound
• Microscopic examination
• Blood or tissue tests
• Bacterial culture

X-rays can show the size, shape, and position of the swim bladder. They may also reveal tumors, deformities, abnormal fluid, or enlarged organs.

Signs the Fish Is Improving

Possible improvement includes:

• Better balance
• Less floating or sinking
• Ability to swim at different depths
• Normal appetite
• Reduced swelling
• Normal waste
• Increased activity
• Fewer scrapes or sores

Continue monitoring because buoyancy problems may return if the underlying cause remains.

Signs the Condition Is Getting Worse

Seek professional help when:

• The fish cannot eat.
• The fish cannot remain upright.
• The abdomen continues swelling.
• The scales protrude.
• Open sores develop.
• Breathing becomes rapid.
• The fish loses weight.
• Several fish are affected.
• The problem continues despite corrected water and feeding.
• The fish appears distressed.

Can a Fish Live With Permanent Swim Bladder Problems?

Some fish can live comfortably with a permanent buoyancy disorder if they can:

• Eat
• Breathe normally
• Rest without injury
• Avoid aggressive tank mates
• Reach different areas of the aquarium
• Maintain a reasonable quality of life

The aquarium may need:

• Shallower water
• Gentle current
• Smooth surfaces
• Easy-to-reach food
• Regular skin checks
• Separate housing

A fish that continually develops sores, cannot eat, or remains severely distressed may have a poor quality of life.

Preventing Swim Bladder Problems

Maintain Good Water Quality

Test regularly and prevent ammonia and nitrite.

Avoid Overfeeding

Offer measured portions appropriate for the species.

Choose Suitable Food

Use food designed for the fish’s natural diet and feeding level.

Keep Temperature Stable

Maintain the proper range for the species.

Prevent Injuries

Use smooth decorations and handle fish gently.

Quarantine New Fish

Observe new arrivals before introducing them to the aquarium.

Choose Healthy Fish

Avoid purchasing fish with severe deformities, abnormal swimming, or obvious swelling.

Common Swim Bladder Treatment Mistakes

Avoid these mistakes:

• Calling every swimming problem swim bladder disease
• Treating without testing the water
• Feeding peas to every fish
• Continuing to overfeed
• Using random antibiotics
• Adding unmeasured salt
• Keeping the fish in an uncycled container
• Ignoring swelling or raised scales
• Assuming the problem is always constipation
• Attaching homemade weights to the fish
• Expecting a permanent deformity to disappear
• Ignoring the fish’s quality of life

When to Contact an Aquatic Veterinarian

Seek professional help when:

• The fish cannot remain upright.
• The condition lasts more than a few days.
• Swelling or pineconing develops.
• The fish stops eating.
• Open sores appear.
• The fish loses weight.
• Several fish are affected.
• The cause is unclear.
• The fish may need an X-ray.
• The fish is valuable or difficult to replace.

Final Thoughts

Swim bladder disorder describes abnormal buoyancy rather than one specific disease. Affected fish may float, sink, tilt, or swim upside down.

Test the water first, review feeding, and look for swelling, infection, injury, or deformity. A brief fast or a change to sinking food may help certain dietary cases, but these steps will not cure every condition.

The swim bladder regulates buoyancy, and persistent problems may require imaging to identify internal changes, as explained by the Merck Veterinary Manual and a veterinary overview of swim bladder disorders.