17 Goldfish Diseases: Identification, Causes & Treatments For Sick Goldfish

“What’s wrong with my goldfish?!” you ask in a panic. “It looks sick!”

Could be.

But before we go on, you should know this up front:

If your goldfish isn’t well, there is a big chance that it actually doesn’t have a disease.

Most goldfish who LOOK sick are really living in bad tank conditions.

(The symptoms are often the same!)

The water may look clean, but it is actually filled with deadly poisons.

Some of these come in through the water you filled the tank with, some are actually made by the fish themselves as they respire and *eherm* go to the bathroom.

Ammonia and nitrite are two major culprits in causing sick fish. Even low amounts will cause irritation, stress and lethargy. But a low pH will cause many other issues because goldfish need the pH to be around 7.4.

Symptoms of water poisoning in goldfish are the exact same as symptoms of other diseases.

So how do you know what’s going on?

There’s a very important step every fish owner needs to take when confronting a problem:

TEST THE WATER

A liquid water testing kit is something every fish keeper needs on hand at all times, especially for emergencies. Think of it as a necessary investment you need to make in order to be a good, responsible goldfish owner. 😉

Check Latest Price

Before you assume your fish needs meds, please test the water or you can end up killing your fish.

So without further ado, here is my complete list of common – and some not-so-common – goldfish diseases, that are actually diseases:

The 17 Common Goldfish Diseases

1. Ich: Did it Snow on Your Goldfish?!

Ich (pronounced “ick”) is a parasite also called “white spot disease.”

The white spots of ich are actually not the parasite itself, but the skin of the goldfish stretching over the parasite.

Outbreaks are very common with new fish that have been stressed, weakened, kept in poor conditions or not quarantined (usually all of the above).

If left untreated, it will kill your fish.

Symptoms

Clamped (flattened down) fins.
Darting and scratching against on objects in the tank, aka “flashing.”
White spots that look like salt granules covering the fish from nose to tail.

Sometimes you might see irritation, lethargy and breathing hard.

If your goldfish has these symptoms, it sounds like you have a case of ich on your hands.

But you should know:

Not all goldfish who do have ich show the classic white speckles. They may just have the behavioral symptoms.

… And not all fish with white spots have ich.

You might see white spots in the wen of an Oranda that aren’t disease-related at all.
Treatment & Prevention:
Most commercial treatments aren’t always able to kick ich.

Fortunately, the cure for ich is pretty straightforward.

It Involves

Raising the temperature up to 80 degrees (F). This will speed up the ich’s life cycle.
Salting the tank by adding the recommended amount of salt dissolved in tank water.
Waiting for 10-14 days and keep the water pristine.

Want to prevent it in the future?

If you have more than one tank, don’t share equipment such as nets or siphons because ich can live out of water (yikes!).

This is just asking for trouble.

And ALWAYS quarantine any new fish you get before introducing them to the others.

Read More: How to Treat Goldfish Ich

2. Flukes: The Invisible Blood-Sucker

Flukes are one of the most common parasites found on goldfish.

In fact, if you have bought a goldfish from the pet store, it is safe to assume it has Flukes – both body Flukes and gill Flukes.

How do they hurt your fish?

They clamp on tight to the skin with spiky hooks and feed on the slime coat, causing the goldfish to constantly bleed until it dies.

And the scary thing about these bad bugs is that you can’t see them! (Without a microscope, that is.)

But it gets worse:

By biting the goldfish, they can inject bacteria into your fish that cause other problems, such as ulcers.

Now, how can you might be dealing with Flukes?

While it takes a microscope to know 100% that your fish has Flukes, you can spot their symptoms. In fact, it is safe to assume that most fish from a pet store are carrying them – they are THAT common.

Symptoms

Goldfish harboring body Flukes will twitch their fins and rub, sometimes bashing themselves on the walls and floors of the tank in an effort to scratch.
Eventually shed their slime coat, trying to rid themselves of the pests.
They don’t want to be around the other fish and clamp their fins.
Sometimes they may get very thin.
Usually fish with body flukes have gill flukes, too.
Gill Flukes causes them to have trouble breathing so they gulp at the surface.

Treatment & Prevention:
Here’s the kicker:

While you can treat the tank with salt and kill some major parasites, there will always be one left behind: the Fluke.

They are salt resistant. Great, right?

So, this means that you are going to have to bring out the big guns and buy your fish some special anti-parasite medication.

I don’t recommend ever using chemical-based medications like Praziquantel or Formalin because they are very dangerous to your aquarium environment and the fish that live in it.

Instead, I treat my new fish that have flukes with MinnFinn.

In the future:

Please don’t wait until your fish are showing signs of a Fluke infestation to treat.

All new fish must be treated for Flukes (unless they have been treated for you by a breeder).

If you don’t want your fish to come down with Flukes, never introduce new fish into their tanks without treating them first.

Always, ALWAYS quarantine.

3. Anchor Worm: Hooked On Your Goldfish

Anchor Worm is a goldfish disease that comes up when the seasons change, usually in the fall.

Because it is so contagious, an entire tank can quickly get infected.

The fish don’t even have to be stressed out to get them.

By the time you actually see the worm, a lot of damage has already been done to the fish.

In many cases, the goldfish have already died or it is too late to reverse the damage done to the remaining fish.

That’s why it’s important to diagnose early.

Especially because place where the worm was stuck on can get infected and kill the fish if it isn’t cleaned.

Symptoms

Flashing (itching) and scratching
Stick-looking worm poking out of it
Where the worm is attached may become very red and bloody

If your fish has Anchor Worm, you will want to stop it in its tracks. How?
Treatment & Prevention:
What you will need to do is remove any worms you can see with tweezers.

Then use hydrogen peroxide to clean the wound. This will help prevent infection.

This is important:

Salt won’t get rid of anchor worm.

Neither will most of the common fish medications on the market.

Only Cyromazine is an effective anti-anchor worm medicine accessible to us fishkeepers.

You will need to treat the whole tank, not just the fish you see the worms on.

Check out our article on goldfish anchor worm treatment.

As far as prevention goes, be sure you don’t add new fish or plants without quarantining them first so they won’t spread disease.

4. Fish Lice: “Flying Saucer” Bugs

The fish louse is more common in ponds than in indoor aquariums. They may be seen in your tank if the fish has been brought in from outside.

It is actually a crustacean-type parasite that lives by sucking blood (ew!).

They spread like crazy, too.

Symptoms

Fish lice are visible little green specks shaped like discs that can be seen hopping around your fish. Usually they show up on stomach, chin and around the fins.
The fish may scratch and itch themselves, leaping and darting around in irritation.
When the case gets really bad, you might see red wounds on the body.

Treatment & Prevention:
Fish lice is resistant to many treatments.

For this pesky parasite, salt won’t work. It’s a lot like anchor worm in that it responds to Cyromazine.

If you don’t want to have lice in your tank, be sure to quarantine all of your newcomers and treat them for parasites ahead of time.

Read the full goldfish lice treatment guide.

5. Velvet: It Doesn’t Feel Soft!

This parasite is also called “Gold Dust.”

Fortunately, it’s pretty rare in goldfish.

It sticks onto the fish by a long needle, causing irritation and other symptoms.

Symptoms

A goldfish with velvet appears to be sprinkled with a fine yellow powder
Starts shedding lots of slime
Starts scratching lots
Other symptoms may include weight loss or clamped fins

Treatment & Prevention:
It’s too bad that salt doesn’t do much to fight Velvet.

That’s why you might have to go for something stronger, like Copper.

The Velvet parasite uses light to live.

So you might also try covering the tank with black paper or cloth to block out the light for a while.

Chances are you probably won’t ever encounter Velvet. But if you want to stay on the safe side, always quarantine any new fish.

6. Trichondia: Hobos in Your Goldfish Tank?

These little guys don’t actually feed on your goldfish.

Instead, they use your fish as a taxi and hotel service combined.

But the parasite stresses your fish, so you don’t want it around.

They are more common in dirty tanks.

In fact, a clean tank sometimes gets rid of them completely without treatment!

Symptoms

Scratching, (also called “flashing”) and irritation
Ulcers from so much itching.
They may stop eating as well

Treatment & Prevention:
You can treat Trichondia with a high concentration of salt, anywhere from 0.3% (which is 3 teaspoons per 10 gallons) to 0.9% (3 tablespoons per 10 gallons).

However, this high of a concentration is extremely stressful to goldfish. In an effort to kill the parasite, you could kill your fish.

Again, MinnFinn can be useful in a case like this.

Preventing this parasite is done through quarantining new fish.

7. Hole-in-the-Head: Who Needs That?!

With a name like that, you know it’s bad.

Most of the time it is an ulcer-causing bacteria and parasite combo attacking the fish during a time of weakness.

Goldfish that have wens (such as an Oranda or Lionhead) may be more prone to this infection.

What’s so dangerous about it?

The bacteria can spread from the outside of the fish to the inside.

Then an internal organ gets destroyed…

… and the fish dies.

Symptoms

This disease often starts out as a little red dot or bloody patch on the head, usually above the eyes.
Over time, the area starts to sink in deeper, pitting and spreading to cause multiple holes.

Treatment & Prevention:
A word of advice:

If your fish has Hole-in-the-Head, chances are that the water is messed up. Bad.

You can do everything you can think of to treat Hole-in-the-Head, but if your goldfish’s environment isn’t right…

… NOTHING you do will help.

It won’t work. Your fish will only continue to go downhill.

Perfect water conditions are absolutely necessary for your fish to heal.

As far as treatment goes:

Swab the hole with Hydrogen Peroxide once.

The antibiotics Furan 2 and Kanaplex used together can knock this out.

Because Hexamita parasites are at play, you also need to treat with Metroplex.

Preventing Hole-in-the-Head much easier than treating it.

Don’t overcrowd your fish.

Do your water changes regularly.

Keep their homes clean and pristine.

8. Fin Rot: The Fin-Eating Disease

A bacteria infection called fin rot is another common goldfish disease.

Like ich, it shows up when the fish is stressed or living in bad water.

But unlike ich, it can be very stubborn and usually takes weeks to get rid of completely.

If you let it go untreated too long, the fish’s fins may never grow back.

How do you know if your fish has fin rot?

Symptoms

Fin rot starts out as a cloudiness on the fins.
Fins get whiter at the tips and begin to rot away, sometimes splitting.
Fins can erode to the base of the tail

By that time, they are PERMANENTLY ruined.

That’s why you want to start treatment as soon as you know it’s fin rot.
Treatment & Prevention:
So your fish has fin rot? Don’t panic – all may not be lost.

If you get to it in time, the damage can be reversed and the fins might heal back.

One danger in treating fin rot is accidentally burning your fish with medications, making the problem even worse.

That’s why I don’t recommend them.

There are a couple other options when it comes to treatment.

A hydrogen peroxide swab offers a much safer route than medications. Dab the affected areas on the fins with a Q-tip dipped in the peroxide every 24 hours.

Or MinnFinn can stop the rot in its tracks.

Really advanced cases might require antibiotics like Sulfaplex to save the fish.

If all goes well, you will start to see black on the rotted areas instead of white. This is a sign of healing.

Preventing fin rot is much easier than treating it. That’s why you should do all you can to avoid running into water quality issues, which are a major cause of this.

9. Mouth Rot: Wait, A Fish Has Gotta Eat!

It could be caused by parasites or bacteria, but in either case mouth rot is a bad deal.

In its later stages, the fish won’t be able to eat, making early detection vital.

Usually the tank is overcrowded, and almost always the water is bad.

Symptoms

Goldfish rubbing its mouth on the sides of the tank or decorations in the aquarium.
Mouth begins to get red. VERY red

Eventually the area starts eroding, until the lips come off, and the mouth caves in on itself. Leaving only a jagged hole.

Pretty nasty, right?

That’s why you don’t want to let it get to that point, starting treatment as soon as possible.
Treatment & Prevention:
Assuming the water quality is perfect, you have some choices when it comes to treatment.

Hydrogen peroxide swabs and MinnFinn have been used with success.

For advanced keepers, antibiotic injections can prove helpful if it is a life-or-death situation.

You should know:

A goldfish with very progressed mouth rot often is left with permanent damage. Often times the fish is no longer able to eat and will starve to death. If your fish is in this situation, it may be best to consider putting your fish to sleep.

Now you know why it is WAY easier to try to prevent fin rot than treat it.

Great water quality and properly stocking your tank are the two most important things you can do to stop your fish from getting this nasty goldfish disease.

10. Ulcers: Ever Growing Holes

These are large red body sores that start off as a patch of red.

The bad news?

They can get large and deep very quickly.

The theory goes that ulcers are caused by flukes, which inject dangerous bacteria into the fish’s skin.

Beware!

If left untreated, the bacteria can spread from the skin into the organs.

Symptoms

Ulcers usually start as an irritated-looking patch of red on the body.
Sometimes the scales may prickle around the area.

(Hint: now’s when you should start treating!)

They can also occur on the head of the fish, often on the ones who have wens.
Shortly, a bloody hole is visible. The hole continues to spread, perhaps bordered with pieces of hanging skin.
Other fish may start nibbling at the wound, making it worse.

Treatment & Prevention:
Because ulcers are bacterial in nature, they need to be treated as such.

Ulcers can kill quickly by many means…

… so the sooner you treat, the better.

How?

In mild cases, this approach can work:

Change the water. Your fish won’t recover in less than perfect conditions.
Scrub the ulcer with hydrogen peroxide on a cotton ball.
Treat with MinnFinn following the instructions on the bottle.

You should know:

It will probably take some time to improve.

Not worse might actually be better, as weird as that sounds.

Overreacting can stress out or even kill your fish, so don’t start doing shotgun treatments out of panic. Stick to the plan.

A healing ulcer may look darker initially, then get lighter each day.

To prevent ulcers, some methods are to be sure to treat for flukes (if you bought a pet store fish) and always, ALWAYS keep the water perfect.

Bad ulcers require a different approach to treatment that I talk about in further detail in my book.

11. Pop Eye: NOT the Sailor Man

Some goldfish have eyes that naturally protrude.

Others are actually sick and need help.

A gross problem some goldfish run into is Pop Eye.

It is more of a signal that something is wrong than a disease itself.

Pop Eye often means there is serious bacterial infection inside the fish.

Symptoms

Eyes of the fish seem to protrude more than usual
One or both eyes may be affected
Eyes begging to they bulge outwards from the head, surrounded by “bags” of fluid
During this phase, they may easily come off
Pop Eye is often accompanied by dropsy or other bacterial infections

Treatment & Prevention:
Adding Epsom salts at 1/4 tsp per 10 gallons can be a good idea. It can help to reduce the pressure behind the eyes.

To fight the infection, Kanaplex is recommended.

Of course, good water conditions are crucial for both treatment and prevention of Pop Eye.

12. Dropsy: The Pine Cone Disease

What is Dropsy?

Basically, Dropsy happens to a goldfish when there is too much fluid inside its body.

Like Pop Eye, it’s a symptom of an internal problem, not the problem itself.

Why is the fish have a problem with its fluids?

There are many possibilities.

If you are always having problems with Dropsy on a regular basis, bad water and/or an improper diet are almost always the main causes.

Bad water weakens the fish and makes it more likely to get a bacterial infection.

A bad diet ruins the internal organs that are in charge of the body’s fluids.

In some cases, parasites inside the fish may be an issue.

Other not-so-common causes include tumors, egg-binding and temperature shock.

13. Cloudy Eye: It’s Kinda Foggy in Here!

Also called White Eye, this condition is most found on goldfish that have protruding eyes.

This is because they are more prone to injury and then infection by sneaky bacteria. The injury that causes Cloudy Eye could also be a burn from ammonia.

Symptoms

Goldfish’s eye begins to look hazy or foggy-lookin
The fish may find it harder to see

Treatment & Prevention:
With a little fish-safe salt (3 teaspoons per gallon), perfect water conditions and time, Cloudy Eye should clear up quickly.

To avoid it in the first place, don’t use decorations with sharp edges and keep the water conditions clean.

14. Fungus: Is there a Fungus Among Us?

Fungus is seen on fish weakened by stress, illness or injury.

A healthy goldfish won’t have fungus.

There are many kinds of fungus that show up in different places.

Here’s the good news:

Nearly all of them have the same symptoms and respond to the same treatments.

What are those symptoms?

Symptoms

White, cottony growths on the body or fins
Fish may act droopy or lose interest in food

On a fish like that Fungus can spread FAST, so you will want to act right away

Treatment & Prevention:
Clean water while you treat for Fungus will make it much easier for your goldfish to recover.

Make sure the water isn’t very cold, too.

Pimafix (a natural anti-fungal medication) will usually bring things back in check.

Fungal diseases are brought on by factors like bad water quality and poor handling.

Knowing this, you can avoid these problems in the future.

15. Tumors: These Bumps are NOT Normal

When cells are multiplying out of control, a tumor is created.

Goldfish can get tumors, too.

And in some cases, they can be cancerous.

They can also grow to get unbelievably huge, FAST. And multiply in number.

Goldfish can get tumors on the inside of their bodies or on the outside.

Some tumors even blind a fish by blocking its eyesight!

It may take a bit, but they DO kill goldfish if left untreated.

That’s why you need to keep reading.

Symptoms

A small lump starts to grow on the fish, usually on the head or body.
The growth may be pink, whitish or even black.
It could be lumpy like cauliflower or smooth.
Sometimes the fish won’t eat or seems depressed.

Treatment & Prevention:
If the tumor is hanging on by a thread, you might be able to snip it off quickly.

Sedating the fish with clove oil can make this easier.

Now I get that not everyone is comfortable with doing this.

That’s when you might need the help of a veterinarian, if you have one in the area that sees fish.

Because exposure to poor water conditions and a diet laced with preservatives in the fish food can cause tumors, keep the water clean as a preventative. Some are caused by a virus so you can’t really do much about that.