Goldfish Cyst – Causes and Treatments

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When it comes to goldfish and most fish in general, diagnosing their various disorders is close to impossible.

This is mainly due to the fact that many conditions share a variety of symptoms and have multiple causes, making it extremely challenging to diagnose and treat them accurately.

Today, we will discuss a rather scary condition that’s commonly seen in goldfish: cysts. What exactly are these, are they contagious, and will they kill your goldfish?

Let’s investigate and find out!

Can Goldfish Get Cysts?

Yes, they can. Goldfish are, awkwardly enough, quite predisposed to developing cysts, many of them without any obvious cause.

This makes the treatment pretty much like shooting arrows in the dark for the most part.

Whatever the case may be, immediate treatment is necessary due to the risk of secondary infections and organ failure, depending on the nature of the cyst.

What Causes Cysts on Goldfish?

Diagnosing the fish’s growths fast is essential since many of them are deadly in the long run.

Depending on their nature, some are also contagious, capable of spreading to other tank inhabitants fast.

That being said, let’s look at some potential causes for your goldfish’s cyst:

  • Bacterial cyst – This is the result of subcutaneous infections, typically resulting from injuries getting invaded by various pathogens. These get under the fish’s skins and multiply, causing small growths that may seem innocuous at first. These require adequate treatment because they can burst, releasing the bacteria into the water and affecting other fish. These types of cysts are easier to address than others that we’ll mention shortly. Some medication may be necessary, depending on your veterinarian’s recommendations.
  • Parasitic cystsIch (White Spots) is the perfect example here. This condition is triggered by a parasite that undergoes 4 developmental phases, one of which is the trophont. This is the pathogen’s adult form, if you will, feeding on the fish’s tissue and forming white spots on its skin. However, these aren’t literal spots but more like small, white cysts that will eventually pop, releasing the organism into the tank. Once free, the trophont will attach to a hard surface and form a capsule to undergo cellular division. The process will eventually force the parasite through several growth phases, the latter being the theront (infectious stage). These will swim into the tank water, looking for a live host to continue their life cycle. Fortunately, Ich is pretty easy to treat, but it requires quarantining the fish first to avoid exposing other goldfish to the parasite. Also, early treatment is key since Ich can be deadly in later phases.
  • Gill hyperplasia – This is a benign condition that could prove deadly nonetheless. It’s generally triggered by gill injuries that get infected by various parasites or bacteria. The place of infection will inflame, sometimes severely, causing respiratory difficulties and visible discomfort. The fish will die in severe cases, and the treatment depends on the condition’s causes. Medication may be useful in this sense, improving the fish’s water quality.
  • Neurofibroma – This is a type of benign tumor, and it’s pretty common among goldfish. They aren’t exactly dangerous since they will only affect the fish’s swimming capabilities and not even that by much. The only problem is that treating them can be a pain in your metaphorical bottom. These growths are well vascularized, as they are deeply implanted in the fish skin and tissue, so removing them is no easy task. Medication is almost never effective, which only leaves you with surgical intervention as the only viable alternative.
  • Chromatophomoras – These tumors are rather rare, mostly seen in Koi and Corydoras, and result from abnormal pigment cell division. They can occur in any type of pigmentation cell, no matter the color they’re producing, and seem to be related to excessive exposure to direct sunlight. Needless to say, these tumors rank as pond cysts for obvious reasons. So, you shouldn’t worry about them if you keep your goldfish in indoor tanks with limited amounts of UV lighting. Goldfish don’t need too much light anyway since they’re used to living in muddy and murky waters in the wild. The treatment may include cryotherapy or surgical interventions in more severe cases.
  • Gonadal sarcoma – This is pretty much a type of cancerous growth that reproduces and can infect the fish’s internal organs. The disorder is most commonly observed in female Koi, but it can be difficult to diagnose since the tumors are internal in most cases. You can only diagnose the sarcoma accurately visually once it’s grown large enough to raise an alarm signal or via radiology or ultrasound. The latter procedures are only useful if you already suspect the tumor’s presence. The treatment should be performed in the disorder’s early phases and usually consists of surgical intervention. Otherwise, the tumor will take over, affecting the fish’s organs and spreading, as cancerous cells tend to do.

Determining the cause of the cyst involves assessing it visually at first.

Although, I would recommend speaking to a veterinarian to get a more accurate diagnosis. This is important since many external cysts may be accompanied by internal growths, either benign or malign, growing on the fish’s organs.

So, there might be more than meets the eye in this case.

When it comes to treating these cysts, there are some procedures available with varying degrees of success. But, as with any other condition, prevention remains the preferred alternative.

The problem is that you can’t really tell which fish is predisposed to developing malign tumors. As a hint, some variations of selectively bred goldfish tend to be genetically prone towards cellular malformations, like the telescopic goldfish, among others.

How to Treat a Goldfish Tumor?

Now that you’ve determined that your fish has an issue, the next step is diagnosing it to know which treatment to apply. In this sense, there are several reliable treatments available, depending on the nature of the disorder:

  • Quarantine – This is a must-have step that many aquarists will ignore due to the extra efforts it comes with. The problem is that you risk infecting the other tank inhabitants by keeping your fish in the main tank, should the tumor prove contagious. Quarantining the fish will not only protect its tank mates but allow for better treatment in a stable and calmer environment. So, always prepare a treatment tank if you’ve decided that your goldfish requires immediate treatment.
  • Ensure optimal water conditions – This is especially necessary for bacterial and parasitic cysts, including Ich. The Ich parasite has a distinct life cycle that takes the pathogen through several developmental phases. Placing the sick fish in a treatment tank and using antibiotics is generally enough to kill the theronts before infecting their new host. Increasing the water’s temperature is also essential since it speeds up the parasite’s life cycle, forcing it to exit the fish’s body sooner.
  • Antibiotics and other medication – These are necessary for conditions like bacterial cysts and bacterial gill diseases, as they kill off the bacteria responsible for the condition. The problem with antibiotic treatments is that they need to be applied in a separate environment not to affect the main tank’s environment. Antibiotics could disrupt your tank’s biofilm, killing Nitrobacter organisms and leading to excessive ammonia buildup, which is lethal for goldfish. So, always ask a vet before using any medication, even after relocating the sick fish into a separate environment.
  • Cryotherapy – This is a popular method of eradicating benign tumors that uses liquid nitrogen to kill off diseased tissue. The therapy works for both external and internal tumors, as the vet can use a cryoprobe to go inside the body, whether immediately under the skin or deeper within the tissue. This procedure will eliminate the problematic growth by causing ice formation at the cellular level, freezing the cells at approximately -40 F. This will generally cut the blood supply to the frozen tissue, causing the cells to die rapidly. Some tumors may even burst due to the ice crystals expanding and rupturing the tissue. You may require several cryotherapy sessions, depending on the tumor’s size, nature, and the body’s own immune system.
  • Surgical interventions – These are primarily necessary for internal tumors that cannot be tackled any other way. The procedure will involve anesthesia, during which a pump will go into the fish’s mouth, oxygenating the fish’s gills and delivering the sedative solution. A typical procedure should last more than 60 minutes, depending on the tumor’s placement, growth, and how difficult it is to remove.

Only a professional can inform you on the right course of action when it comes to fish tumors.

Distinguishing between benign and malign ones is a matter of in-depth investigation, given that many tumors are similar in appearance.

How Long Can Goldfish Live with a Tumor?

The answer depends on the tumor’s size, placement, whether the treatment has been effective or not, the fish’s age and health status, etc.

If your fish doesn’t face any complications during the treatment and the procedure is successful in removing the tumor, the patient could make a full recovery.

It’s not uncommon for goldfish to live normal lives for years following the treatment if everything goes according to plan.

You should also remember that malign tumors may bounce back, which will make them even more difficult to treat the second time around.

Other than that, your goldfish should be fine, provided the treatment is effective, and the fish is healthy with a strong immune system.

Make sure to provide your goldfish with adequate and stable water parameters throughout the treatment.

This will prevent any infections and complications following the surgical intervention, keeping your goldfish healthy and comfortable during the recovery phase.

Are Goldfish Cysts Contagious?

It depends on their nature. Bacterial cysts may be contagious, and so is Ich. This is what makes prevention and early diagnosis so important when it comes to conditions like these.

Allowing you to detect the cyst in time and quarantine the goldfish immediately will greatly reduce the spreading risk.

This means you should always have a backup tank ready for emergency cases like these.


Goldfish are hardy creatures, capable of bouncing back from any condition, so long as the treatment is effective.

I recommend several things to help them battle their health issue:

  • Monitor your goldfish and act fast – You should act as soon as you notice any change in the fish’s behavior or observe any skin growth or unusual color changes. Even the most severe tumors and health issues appear completely innocuous at first. The first step – is quarantine. This will place the goldfish in a controlled and stable environment for treatment, protecting the other fish in the process.
  • Ensure optimal water conditions – Monitor water parameters, perform regular water changes, preferably every other day, and keep the temperature and other water parameters stable. Your goldfish should receive nutritious meals during a fixed dietary schedule to strengthen its immune system and help fight the disorder.
  • Contact an expert – Forget the internet. Diagnosing the condition yourself is almost always bound to fail, especially if you’ve never faced anything similar before. Contact a competent veterinarian to make sure you’re not using the wrong treatment, which could allow the disorder to progress uninhibited.

After all, is said and done, keep in mind that fish tumors aren’t always curable. In fact, most of the time, they’re not, especially sarcomas.

Euthanasia is often the answer to spare the fish of unnecessary suffering and protect the rest of the goldfish population.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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