17 Common Goldfish Diseases, Diagnosis & Treatment

Goldfish are a popular choice for both novice and experienced aquarists, but these delightful creatures can fall prey to various health issues. Understanding the most common goldfish diseases is crucial for keeping your aquatic companions healthy and vibrant.

We’ll be looking at 17 diseases and illnesses commonly associated with goldfish, the causes, treatments, and how to prevent them.

I am not a vet and any advice given on this page is based on my experience.

I always recommend consulting a qualified veterinarian for the best treatment options.

If you need to find a specialist fish vet in your local area you can do so here:
– https://fishvets.org/find-a-fish-vet/
Global – https://www.wavma.org/find-a-fish-vet

Poor Water Quality – No.1 Cause!

Maintaining good water quality can prevent most Goldfish diseases and illnesses.

When you spot any worrying signs in your goldfish tank, the first thing you should always do is check the water parameters as most times something will show up that you need to fix.

The only kit I use for this is the API Freshwater test kit as it’s much more accurate than paper test strips.

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If nothing shows up on the test kit, you need to check you have the correct tank setup for goldfish, as not having the optimum setup can cause stress, which lowers their immune system, which then leads to disease outbreaks.

Always Quarantine New Fish & Plants

Closely followed by poor water quality, not quarantining new fish and plants is an almost guaranteed way of introducing nasties into your aquarium.

You’ve no idea where the new fish or plant has been kept and what horrors it may be harboring, even fish that look healthy can have underlying issues.

Always quarantine new arrivals before adding them to your main tank.

4-6 weeks is recommended as some disease symptoms can take up to 4 weeks to appear.

17 Goldfish Diseases & Illnesses

Now we’ve gone over the main causes of disease and illnesses in a goldfish tank, we’ll dive into the different disease symptoms and treatments.

1. Anchor Worm

An anchor worm is a parasitic infection in goldfish caused by a crustacean parasite from the Lernaea species.

These parasites attach to the fish’s body, causing inflammation, red sores, and potentially secondary infections.

Anchor worm treatment involves a veterinarian removing the worms while the fish is sedated.

Organophosphates or diflubenzuron can be effective treatments, but they must be used with caution due to their potential toxicity.

Regular observation of fish for early signs of infection can also help in taking prompt action to manage an outbreak.

2. Buoyancy Disorders

Goldfish are susceptible to disorders that affect their ability to control their buoyancy, experiencing either difficulty in sinking or floating.

As physostomous fish, they possess a unique connection via a pneumatic duct between their swim bladder and esophagus, which enables them to gulp air and regulate the swim bladder’s inflation. Additionally, a specialized gland known as the oval plays a crucial role in releasing any surplus air.

Disorders related to excessive buoyancy are most frequently observed post-feeding.

Goldfish, the labrador retrievers of the fish world, are prone to ingesting too much air when they feed enthusiastically at the water’s surface.

This air can accumulate in either the gastrointestinal tract or the swim bladder. Typically, the fish will return to its normal state once it expels the extra air.

However, if the oval gland malfunctions, it can lead to persistent issues with buoyancy that may necessitate surgical intervention to resolve.

On the other hand, issues with sinking, or negative buoyancy disorders, tend to arise as a result of stress or an inadequate diet.

Essentially, the fish may lack the drive or strength to swim properly. By addressing the underlying stress factors and ensuring the fish receives a nutritious diet, normal behavior is usually restored.

It’s important to note that external devices designed to act as “wheelchairs” for fish can be extremely harmful and pose a serious risk to their well-being.

3. Carp Pox

Carp pox, also known as fish pox, is a condition in goldfish and other carp caused by the Cyprinid herpesvirus 1.

Common signs of carp pox are waxy, white to pinkish growths or lesions on the skin, fins, and occasionally gills of affected fish.

The condition is more common in cooler water temperatures and often seen in young fish, as they have not yet developed a strong immune system.

There is no known cure for carp pox. Once your fish has it, they have it for life.

You have a few options for managing the symptoms. The lesions may regress on their own as water temperatures rise, and maintaining optimal water conditions can help support the fish’s immune system.

Alleviating symptoms by raising the water temperature may help the fish combat the disease.

Since the virus is spread through contact with infected fish, it’s important to quarantine new additions to the pond or aquarium to prevent the introduction of the virus.

4. Cloudy Eyes

Cloudy eyes is a condition where the eyes appear milky or opaque.

According to cafishvet.com, the most common cause of cloudy eyes is injury or trauma, but other causes include poor water quality or bacterial infections.

Fish with protruding eyes, such as the telescopic and celestial eye goldfish are more prone to injuring their eyes.

Treatment for cloudy eyes typically involves addressing the root cause. If poor water quality is to blame, improving the water conditions by performing regular water changes and ensuring good filtration is crucial.

If an injury is to blame, remove any sharp objects or decorations from the tank.

Regular monitoring of water parameters and setting up a goldfish tank correctly, by avoiding sharp objects can help catch and address issues before they lead to conditions like cloudy eyes.

5. Cotton Wool Disease 

Cotton wool disease aka cotton mouth in goldfish, is caused by the bacteria Columnaris, it manifests as white, cotton-like patches on the skin, mouth, or gills. 

It can spread rapidly and is sometimes mistaken for a fungal disease due to its appearance, don’t waste your money on anti-fungal treatments, they won’t work!

Treatment for cotton wool disease starts with finding the root cause and addressing that issue first, is the water quality good and are you feeding your goldie a high-quality varied diet?

It may clear up by itself, but if it doesn’t you should contact a vet for some strong antibiotics that aren’t available OTC.

6. Fish Lice

Fish lice are caused by a parasitic crustacean called Argulus, which attaches to the fish’s skin and feeds off the bodily fluids….mmmmmm tasty!

This causes irritation, inflammation, and potentially secondary infections.

These parasites are visible to the naked eye and can cause the goldfish to scratch against objects due to discomfort.

To treat fish lice, a vet can physically remove some of the parasites using tweezers.

OTC meds will only work on the juvenile stages of this parasite, if this parasite is more advanced you’ll need to consult a vet to find a suitable medication.

To help prevent fish lice you should quarantine all new fish.

7. Fin Rot

Fin rot is a common bacterial infection that results in the deterioration or fraying of the fins and tail.

It often starts at the edges, which may appear ragged, and can progress to more severe tissue damage if untreated.

The first step of treatment is to check the water parameters and clean the tank if necessary, swimming in a toilet with a skin infection isn’t going to help your goldie recover!

Antibacterial medications, such as Kanaplex can help, or for more serious infections consult a vet for the appropriate treatment.

8. Flukes

Goldfish flukes are caused by microscopic parasitic flatworms that attach to the gills, skin, or both.

These parasites are microscopic and the first sign of them will be when your goldfish is behaving strangely.

Flukes cause irritation which may cause your fish to rub itself against things (aka flashing), respiratory distress, and increased susceptibility to secondary infections.

To treat flukes, you typically use anti-parasitic medications like praziquantel, which can be administered in the water. API General Cure can be used to treat flukes.

It’s important to follow the recommended dosage and treatment duration to ensure all life stages of the flukes are eradicated. In some cases, multiple treatments may be necessary.

9. Ich (AKA White Spot Disease)

Ich, also known as white spot disease or Ick is caused by the parasite Ichthyophthirius multifiliis.

It’s one of the most common diseases in fish and is recognizable by small, white, grain-like dots on the skin, gills, and fins.

Treatment of ich involves raising the tank’s temperature gradually to speed up the parasite’s life cycle and using a medicated treatment like Aquarium Solutions Ich-X.

An aquarium salt bath can also be effective.

It’s important to treat the entire tank because the ich parasite is present in the water, not just on the fish.

10. Neurofibromas (AKA Warts)

Neurofibromas in goldfish are nerve sheath tumors that manifest as localized lumps on the skin and fins.

These tumors are typically benign but can grow quite large and potentially hinder the fish’s mobility or organ function.

If your goldfish is behaving normally and doesn’t seem stressed, it’s common for them to live a normal life with these bumps, they don’t look great but if it’s not impacting their daily life treatment isn’t usually required.

Treatment of neurofibromas in goldfish is challenging. Surgical removal is an option, but it is only a temporary fix as these tumors tend to be highly infiltrative into the skin and may recur.

In some cases, cryotherapy has been attempted, but there is limited information on the long-term success of this treatment for fish.

Preventing neurofibromas is difficult as the exact cause is not well understood.

Maintaining a healthy environment for your goldfish with optimal water conditions and a balanced diet may help reduce the risk of tumors developing.

11. Polycystic Kidney Disease

Goldfish can suffer from a condition where cysts develop in their kidneys, leading to organ failure and significant harm to the tissues.

The origins of this ailment are unclear, and currently, there is no known cure.

Similar to many other animals, once a goldfish’s kidneys are impaired, they cannot regenerate.

The physical symptoms of polycystic kidney disease in goldfish often include a noticeably swollen abdomen, making the fish look as if it has swallowed a water balloon.

Unfortunately, there is no cure, although your vet may be able to drain the fluid to make your goldfish more comfortable, this is only a temporary solution.

12. Ulcers

Goldfish ulcers are open sores that can appear on the body, often as a result of bacterial infections like Aeromonas or Pseudomonas.

These ulcers can be exacerbated by poor water quality, stress, or injury.

To treat ulcers, first, improve the water conditions to prevent further infection, swimming in poop-filled water isn’t great for open wounds!

This alone should see an improvement in the mildest ulcers.

For severe cases, you should consult with your vet as they may need to prescribe antibiotics.

Non Diseases

There are a few things that people think are diseases that aren’t, they are symptoms of an underlying issue.

13. Dropsy

Dropsy isn’t a disease but rather a symptom indicating that the kidneys are being adversely affected by some underlying problem.

A variety of health issues can lead to the condition known as dropsy in fish, which is characterized by edema (fluid accumulation) in the body tissues. 

Factors such as poor water conditions, insufficient nutrition, aggression from other fish in the tank, growths, and infections from parasites, viruses, or bacteria can all contribute to this syndrome.

Persistent stress from these or other sources can weaken a fish’s immune system, making it more susceptible to opportunistic infections from their surroundings.

14. Popeye

Popeye is generally caused by trauma and can cause protruding, bulging, or swollen eyes, but it can also be caused by other underlying health issues.

Fancy goldfish with protruding eyes, such as telescopic and celestial eyes are more prone to getting popeye.

Popeye can affect both eyes (bilateral) or just one eye (unilateral) and treatment can vary based on the underlying cause.

Usually, trauma will affect one eye and an underlying issue will affect both eyes, but there’s no guarantee that this will be the case.

For treating popeye caused by trauma, removing the cause of the trauma is the first port of call, so any sharp objects or aggressive tank mates should be removed.

For underlying causes of popeye, first (as always) is to check the water conditions are optimal and fix if not. 

If they are good, you need to figure out the underlying issue, which is usually a kidney or gill problem that is causing the goldfish to retain excess fluids, which in turn can cause the eyes to bulge.

15. Red Streaks on Skin & Fins

Seeing red lines on the skin and fins of your fish often indicates stress or suboptimal water conditions. It can also be caused by a bacterial infection, which presents itself as red blotches under the skin or on the mouth.

Upon noticing this, it’s crucial to promptly test the water parameters. If you find any discrepancies from the ideal levels, rectifying the water quality might clear up the red markings.

Should the water tests show normal results and you haven’t made any significant alterations to the tank recently, the next step is to pinpoint what’s causing stress to your fish.

Pinpointing the issue can be hard, a couple of things to watch out for are: Does your goldie appear stressed, or is it getting bullied by other fish and hiding?

If this isn’t the case, then bacterial septicemia could be the issue, which needs to be treated quickly with an antibiotic such as KanaPlex.

16. Swim Bladder ‘Disease’

Swim bladder disease, something that fancy goldfish are particularly prone to, is another that is mislabeled as a disease.

Swim bladder disorder can be split into 2 issues, positive buoyancy disorder, which is when your goldfish appears to be stuck at the surface or floating upside down, and negative buoyancy disorder is when your goldfish is stuck at the bottom of the tank.

It could caused by anything from ingesting too much air when feeding at the water’s surface, poor water quality, to an actual problem with your fish’s swim bladder.

It may correct itself within 1-2 hours of your goldfish eating, if it doesn’t there may be a more serious underlying issue.

You should consult with a vet to get a proper diagnosis of what’s causing your fish’s swim bladder disorder before starting any treatment.

17. White Stringy Poop

White stringy poop coming out of a goldfish is a bowel movement without any food in it.

It can be alarming when you see this, as it looks like a big worm coming out of its butt!

A goldfish’s metabolism doesn’t speed up if they eat more food. How fast it runs depends on the water temperature.

Warmer water = faster metabolism = more pooping.

If your water is at the warmer end of what goldfish can be kept in and your goldie isn’t eating often enough, you’re going to see them passing white stringy poop regularly.

This has a simple treatment plan: turn down the water temperature and feed them more often.

Closing Thoughts On Common Goldfish Diseases

Most goldfish diseases and illnesses can be avoided by making sure your tank is kept clean and well-maintained, with the correct water parameters for goldfish, by feeding a high-quality varied diet, and by quarantining new fish, invertebrates, and plants for 4-6 weeks.

Even the most vigilant fishkeepers can end up with an outbreak from time to time, so hopefully this guide will help you identify and treat the issue quickly.

If you would like to seek veterinary advice you can find a specialist aquatic vet in your area using the links below:

Check out the Aquarium Health section for more guides just like this one and keep your fish tank in tip-top shape.



Hey, fellow fish enthusiast 👋! I'm Paul and I've been an aquarium addict since I won my first goldfish at the fair many years ago. Let me share with you the knowledge that I've gained along the way (and avoid the mistakes I've made!), so you too can create an underwater paradise for your aquatic friends.