Goldfish Warts – What Causes Them and How To Treat Them

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So you’ve seen some lumps or bumps growing on your goldfish and are worried about their health.

The good news is that most wart-like growths on goldfish are completely benign cutaneous tumors that won’t affect your pet fish’s health.

What Are the Lumps on My Goldfish?

The lumps and bumps on your goldfish are very unlikely to be caused by a virus in the manner that true warts are.

Although they may appear to look like warts, the growths appearing on your goldfish’s skin are almost certainly a benign cutaneous tumor – specifically a nerve sheath tumor.

These tumors can grow anywhere on the fish’s body and can range from tiny bumps that are a few millimeters across, to large lumps that are more than an inch in diameter.

Being termed as benign means that this type of tumor isn’t harmful to your goldfish, and won’t directly affect their health. They are also not contagious to other fish or humans.

But the Lumps Are Unsightly!

Well, yes. Although these lumps are perfectly harmless, they do of course affect how your goldfish looks.

While some of these tumors may be fairly inconspicuous, others can grow large and make a big impact on your goldfish’s appearance.

Try to remember that a goldfish is for life. While most pet fish will live for less than 10 years, goldfish usually exceed this and have even been known to live for over 40 years!

Just like us, a goldfish simply won’t always look as pretty and youthful as when you first bought it, so my advice is to try to love your goldfish as it is, with lumps, bumps, and all of its beautiful imperfections!

Some goldfish owners have, however, decided the lumps are so unsightly that they’ve resorted to taking their fish to have the tumors surgically removed by a vet. There are, however, some potential problems with this.

Removing the Tumors

Before considering having your goldfish’s growths removed, it’s important to know that surgical excision of these benign tumors is only a temporary fix – they will grow back.

This is because the tumors are lodged deeply within the fish’s tissue and can never be removed entirely. Whatever is left of the tumor will eventually grow back, meaning you’ll be stuck with the same problem as before.

It should be needless to say that catching your fish, taking it to the vet, having it cut open under anesthetic, and then left to heal a large wound will cause your fish a great deal of stress.

The unsightly wounds left behind from the surgery could also become infected with bacterial or fungal infections, thereby making a benign problem a life-threatening one.

Some vets have also attempted cryotherapy (applying liquid nitrogen) on goldfish with benign tumors, but once again, the results are only temporary and the wart-like growths will come back.

Besides, the growths will sometimes fall off by themselves.

Why Are My Goldfish Warts Falling Off?

When goldfish ‘warts’ (benign tumors) grow larger, they can create a lot of drag as the goldfish swims around the fish tank. With enough time, the water resistance pulling on the growth can make the wart fall off.

This may be a temporary relief to see your goldfish swimming around without a big lump hanging off them, but once again, it won’t last forever.

Since the tumors are deeply embedded in the fish’s tissue, the growths will eventually return. With enough time they may even grow large and repeat the cycle all over again!

Could My Goldfish Warts Become Infected?

Although nerve sheath tumors are harmless to goldfish, they could become infected if they are removed, fall off, or become damaged. Bacterial and fungal pathogens can lie dormant in the aquarium water, waiting for a weak fish or an injury to infect.

Goldfish Warts

If you notice the growth becoming red, swollen, or discharging white liquid, it’s probably become infected and will require treatment to prevent it from spreading to the rest of the fish’s body.

Antibiotic treatments, either given to your fish in their fish food, in a bath, or applied topically are the professional treatment for bacterial infections. Depending on your local regulations, you may need to obtain a veterinary prescription to get them.

Preventing infections in aquarium fish is always better than trying to treat them, though. Keeping your tank clean, your water quality high, and providing your fish with a safe, nurturing environment are the keys to ensuring sanitary conditions and strong immunity in your fish.

Could My Goldfish Warts Be Carp Pox?

You may have heard that goldfish can contract a contagious disease known as ‘carp pox’ or ‘koi pox’. Carp pox is a viral disease in fish caused by a herpes virus that causes milky skin lesions on freshwater fish belonging to the carp family – which includes goldfish.

But while carp pox may sound similar to warts, the symptoms are very different. The lesions or small bumps created by the virus are always a white, milky color and don’t resemble the tumors that we’ve been speaking about.

Although there is no known cure, carp pox is not a deadly disease and symptoms will simply come and go depending on how successful your fish’s immune system is at fighting it off.

Sadly, it can lead to secondary infections and cause problems if it develops near the fish’s gills or eyes.

Thankfully, carp pox is not contagious to humans!


Goldfish ‘warts’ are usually not warts at all, but benign nerve sheath tumors that cause lumps to develop on your goldfish’s body.

Although unsightly, these tumors are harmless in themselves, and attempting to remove them may sometimes do more harm than good.

If your goldfish’s growths become infected, however, you’ll need to treat them promptly to prevent the infection from spreading.

To find out more about fish health and diseases, be sure to check out our dedicated pages here.

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