7 Most Common Goldfish Diseases & How to Treat Them

Goldfish are captivating, low-maintenance pets, but they’re not immune to a variety of diseases that can jeopardize their health and well-being—especially if not cared for correctly. And while some diseases are curable, others unfortunately, aren’t. This is why it’s so important to detect diseases early on, so you can promptly intervention and take action. 

We, along with ex-zookeeper Andrew Silver, explore the most prevalent goldfish diseases, their signs and symptoms, and effective treatment options, ensuring that you’re well-equipped to keep your beloved finned friends happy and healthy.

Key Takeaways

  • Observing goldfish regularly and recognizing signs of common diseases is essential for timely treatment.
  • Maintaining optimal water quality, using aquarium salt & avoiding overcrowding are key elements in preventing the spread of diseases.
  • Quarantine protocols combined with proper diet & minimized stress are necessary to ensure fish health.

Identifying Goldfish Diseases

Early intervention and treatment can make all the difference in your goldfish’s prognosis. In order to detect diseases, observe your goldfish regularly, paying close attention to their appearance, behavior, and swimming patterns. A keen eye can spot any changes that may indicate the onset of a disease.

By understanding the causes of these diseases and recognizing their signs and symptoms, you can take swift action to treat affected goldfish and prevent the spread of illness among the rest of your aquatic community.

How Do You Tell if a Goldfish Has a Disease?

While goldfish can be affected by various diseases, many share similar signs and symptoms. 

  • Changes in your goldfish’s appearance, such as white spots, missing scales, discolored gills, or frayed fins, can indicate a bacterial or fungal infection. 
  • Behavioral changes like rapid breathing, lethargy, or unexplained aggression can also be warning signs of an underlying health issue.
  • Swimming patterns can reveal a lot about a goldfish’s health, as well, like erratic or spiral swimming, shimmying, or struggling to maintain their balance.
  • In the case of parasitic infections, such as flukes, goldfish may exhibit “flashing” and flick against objects in the tank due to skin irritation. 

If you suspect your goldfish is ill, it’s best to take it to a veterinarian who specializes in fish health. They’ll be able to diagnose the problem and provide the best treatment for your fish.

Causes of Disease

Goldfish diseases can stem from a variety of causes. Commonly: 

  • Poor water quality
  • Poor diet
  • Overcrowding
  • Stress
  • Exposure to parasites or bacteria

Ensuring your fish are in a healthy environment and minimizing stressors can help prevent the onset of diseases.

Some goldfish diseases, such as fungal infections, are more likely to affect fish that are already weakened due to stress or illness. In these cases, early detection and treatment will help prevent their spread and improve the goldfish’s chances of recovery, especially since they aren’t considered hardy fish.

“Poor water quality is the most common cause of disease,” says Silver. “You can maintain the water quality by providing your goldfish with plenty of space, not overfeeding, and doing partial water changes weekly.”

What Are the Most Common Goldfish Diseases? 

“Some of the most common goldfish diseases include buoyancy disorder [like swim bladder disease], parasites [like flukes], cloudy eyes, and neurofibromas,” Silver says. “Poor water quality is the most common cause of disease.” 

Here are a few more common goldfish diseases, their symptoms, causes, and treatment.

Swim Bladder Disease

Swim bladder disease can greatly impact goldfish’s buoyancy and swimming ability and can be caused by a combination of factors such as poor diet, stress, and genetic predispositions.

Symptoms of swim bladder disease include:

  • Difficulty swimming
  • Floating upside down
  • Sinking to the bottom of the tank. 


The causes of swim bladder disease in goldfish can vary and may include factors such as:

  • Poor diet
  • Stress
  • Genetic predispositions

Fluid buildup in the swim bladder, for example, can be attributed to ingestion through the fish’s diet or due to bacterial or parasitic infections.

Identifying the underlying cause of swim bladder disorder will help you determine an effective treatment plan and prevent further complications.

🐠Learn more about swim bladder disease in tropical fish.


Treatment for swim bladder disease typically involves addressing the underlying causes, such as improving water quality and providing a balanced diet. 

“[Swim bladder disease] is normally temporary and can be treated by feeding your fish food that sinks to the bottom of the tank,” says Silver.

Isolating the affected goldfish in a quarantine tank, maintaining optimal water quality, and reducing stress factors are effective treatment plans for swim bladder disease.

Fin Rot

Fin rot is a bacterial infection that affects the fish’s fins, particularly goldfish.

The edges of the goldfish’s fins appear white or cloudy. As the infection progresses, the fins may become progressively shorter, with dead tissue falling away and leading to inflammation and redness of the affected area. In some cases, bloody areas may also be present.

🐠Learn more about fin rot and how to spot and treat it.


Fin rot is typically caused by factors such as poor water quality, inappropriate water temperature, overcrowding, and stress. 


Treatment involves improving water quality by doing a water change, using aquarium salt, and reducing overcrowding. You may use antibiotics, such as erythromycin or tetracycline

Cotton-fin Fungus

Fungal infections in goldfish can cause white, cotton-like growths on the fish’s body and fins. 

🐠Learn more about the signs and symptoms of cotton fin fungus.


These infections are often the result of stress, injury, or illness, and can lead to serious complications if left untreated.


Treatment and prevention of fungal infections in goldfish involve maintaining good water quality, reducing stress, and using antifungal medications when necessary. Regular water changes, gravel cleaning, and filter maintenance can help create a healthy environment for your goldfish, minimizing the risk of fungal infections.


Ich is a parasitic infection that causes white spots on the goldfish’s body and can be potentially fatal if not treated in a timely manner. 

🐠Learn how to cure ich, fast.


Ich is often present in the aquarium, but it typically only becomes apparent when the fish are weakened due to stress or inadequate water conditions.


Treatment involves medicating the water with potassium permanganate, salt baths or dips, and using anti-fungal medications such as Methylene Blue or Malachite Green until the infection is eradicated.

Anchor Worms and Fish Lice

Anchor worms and fish lice are parasites that burrow into the goldfish’s flesh, resulting in tissue damage and discomfort. Symptoms may include white spots on the body and burrowing into the flesh, resulting in tissue damage and discomfort.


Anchor worms are most commonly found in fish that are kept outside in ponds, while fish lice are generally linked to pond fish that have been transferred to an aquarium environment.


Treatment for anchor worms and fish lice involves the use of appropriate antiparasitic medications.

Hole-in-the-Head Disease

Hole-in-the-head disease is a condition that affects the head of goldfish, causing sores on the fish’s head that turn into tube-like structures filled with mucous. 


Hole-in-the-head disease is caused by a parasite called hexamita, which naturally exists in the fish’s gastrointestinal tract. At low levels, they’re harmless but when the fish’s immune system is weakened (often due to poor water quality for prolonged periods of time) the parasite spreads through the body. This disease can lead to serious tissue damage and discomfort for the affected fish.


Hole-in-the-head is serious, but treatable with Aqua-Zole.


Dropsy is a condition where goldfish look bloated due to fluid accumulation. The bloated appearance can be distressing for both the fish and its owner, and treatment can be challenging as the underlying causes may vary.

🐠Related: Dropsy in fish: Causes, Symptoms, and Treatment.


Dropsy is often caused by poor environment, leading to a weakened immune system and infection.


Addressing poor water quality, providing a balanced diet, and administering antibiotics like API Melafix when necessary can help alleviate dropsy and improve the goldfish’s condition.

Quarantine and Prevention Measures

Quarantine and prevention measures are essential for maintaining goldfish health and preventing the spread of diseases. Implementing a strict quarantine protocol for new fish, can help minimize the risk of introducing diseases to your aquarium.

Diet plays a preventive role, too. 

“Goldfish are omnivores, so it is important to give them a varied diet that is both plant and protein-based. A varied diet will help prevent nutritional deficiencies,” Silver says.

Maintaining Proper Water Quality

To ensure optimal water quality for goldfish, I recommend regular water changes, testing the water for ammonia, nitrite, and nitrate levels, and avoiding overfeeding. Additionally, incorporating an air stone or bubbler can help maintain adequate oxygenation of the water.

Proper filter maintenance and gravel cleaning can also help prevent the buildup of waste and harmful substances in the aquarium, contributing to a healthy environment for your goldfish.

Aquarium Salt

Aquarium salt can be used as a preventive measure against various goldfish diseases, as it helps maintain a healthy environment. Aquarium salt adds electrolytes to the water and acts to prevent bacteria and other pathogens.

Make sure to use aquarium salt specifically formulated for aquariums, as other types of salt may contain impurities that can be detrimental to fish.

Signs a Fish Is Dying

Signs that a fish may be dying include difficulty breathing, erratic movement, pale color, and loss of appetite. These symptoms may be due to incorrect environmental conditions, stress, or injury.

Remember, fish can also die from old age.

Detect and Prevent Disease in Your Goldfish 

Remember, a healthy goldfish is a happy goldfish. Goldfish can be susceptible to a variety of diseases that can jeopardize their health and well-being but early detection, proper diagnosis, and timely intervention will help prevent the spread of disease and ensure your goldfish’s continued happiness and health. 

A final word of advice from Silver for first-time goldfish owners:

“Avoid the traditional goldfish bowls. Give your goldfish plenty of room, offer a varied diet, and maintain the water quality.”

Frequently Asked Questions

What Does Bacterial Infection Look Like on Goldfish?

Signs of a bacterial infection in a goldfish may include:

  • Reddening of the body
  • Hemorrhagic spots
  • Skin and gill ulcers
  • White film
  • Cloudy eyes
  • Tattered fins
  • Bloody patches or open sores on the body and mouth

These symptoms can be indicative of a bacterial infection, and should be treated as soon as possible to prevent further damage to the fish. Treatment may include antibiotics, water changes, and improved water quality.

What Diseases Can Goldfish Give Humans?

Humans can contract various bacterial infections from contact with goldfish, including:

  • Mycobacterium
  • Erysipelothrix
  • Campylobacter
  • Aeromonas
  • Vibrio
  • Edwardsiella
  • Escherichia
  • Salmonella
  • Klebsiella
  • Streptococcus iniae.

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