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?

Symptoms:

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.

• 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.

Read More: Goldfish Flukes Symptoms, Treatment & Diagnosis

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:

The first symptoms are flashing (itching) and scratching.

Then all doubt goes away when the goldfish gets a nasty, 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.

Here’s something else:

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.

This gives the fish a “velvety” appearance.

Your goldfish might also start shedding lots of slime to get rid of the parasite…

…or scratching on things to dislodge them.

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 is a symptom of Trichondia.

Over time, the fish may get 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.

It doesn’t take long before the fins get whiter at the tips and begin to rot away, sometimes splitting.

Eventually the 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:

Initially, you might notice your goldfish rubbing its mouth on the sides of the tank or decorations in the aquarium.

Then the 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:

1. Change the water. Your fish won’t recover in less than perfect conditions.
2. Scrub the ulcer with hydrogen peroxide on a cotton ball.
3. 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:

You may first notice the eyes of the fish seem to protrude more than usual.

One or both eyes may be affected.

Sometimes very rapidly, 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.

Read more about Dropsy treatment here.

Symptoms:

Dropsy shows itself in two main ways:

• Extreme swelling in the belly, like a hot air balloon.
• Or scales standing out all over the body, like a pine cone.

You may also see Pop Eye present.

How do you treat Dropsy? Is there even a cure?

Treatment & Prevention:

I wish I had better news…

But by the time you can tell your fish has dropsy, 99% of the time… IT’S TOO LATE.

This is because there has been some kind of internal damage. And once the organs inside the fish have been destroyed, there is no turning back the clock.

A fish may last a few days to a few months before it dies.

For a fish that has Dropsy and Pop Eye, the case is always terminal.

Not good.

Because of the high mortality rate, it may be the kinder thing to opt for euthanasia rather than treatment.

What makes treating Dropsy so difficult is that many times you don’t know what caused it. Remember, it’s a symptom, not a disease.

Here is something you can try:

If a bacteria infection is causing the Dropsy, antibiotics may prove useful.

Epsom salts might help to ease the pressure from fluid buildup.

But treatment won’t help in less than perfect water.

So:

How can we avoid this horrible condition?

The best way to prevent Dropsy is by keeping the water quality good at all times, feed sparingly and don’t overstock, though dropsy has many different causes even outside of these.

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:

Just like it sounds, this disease makes the normally clear lens of a goldfish’s eye hazy or foggy-looking.

The fish may find it harder to see.

Cloudy Eye can be found alongside other symptoms, too.

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 are a sure sign that your fish has Fungus.

If the case is really bad the 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:

It’s easy to tell when a goldfish has a tumor.

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.

16. Carp Pox: Warts that Don’t Come from Toads

Viruses in goldfish are becoming more common.

Carp Pox is one of them.

It is usually seen on goldfish kept in ponds, or even in aquariums.

Nobody knows how it spreads.

And this is good:

Carp Pox WON’T kill your goldfish.

Want to know the weird part?

It can totally disappear only to come back later!

Symptoms:

Carp pox looks like smooth, white or pinkish “warts” on the edge of the fins or on the body.

Treatment & Prevention:

There is no absolute cure for Pox…

… And there’s not really a way to prevent it either.

But if you’re desperate, here’s something you can try:

Put the fish in warm water in a bath of at least 80 degrees for a while. Adding a fish-safe salt may help.

17. Lymphocystis: The Stressed-Out Virus

Like so many goldfish diseases, this virus attacks a weak and stressed fish.

It’s similar to Carp Pox in just about every way.

Symptoms:

The fish will have white, crusty lumps growing on (usually) the edge of the fins or even on the scales.

These “tumors” are shaped like a cauliflower.

Treatment & Prevention:

Bathing the goldfish with a chemical called acriflavine is recommended.

With any luck, they will go away in a short time.

Because it is a mystery how goldfish viruses spread, the best way to prevent them is to keep the water clean.

Learn Something? Pass It On!

I know you have a ton of questions I didn’t cover in this post.

I’d love to hear your success story at treating one of these goldfish diseases!

It doesn’t have to be an earth-shattering insight. Even a helpful story would be awesome.

So leave a comment right now with something you want to share.

But before you do…

Are struggling with this whole “goldfish thing” and feeling a bit lost?

Or want to learn emergency CPR for your goldfish, and the biggest mistake most people make when they encounter a problem?

Good news.

You can learn exactly what you need to do in The Truth About Goldfish eBook: