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17 Common Goldfish Diseases: Symptoms, Causes & Treatments

Lindsey Stanton Profile Picture

By Lindsey Stanton

“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.

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 copy

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.

  • 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
  1. Raising the temperature up to 80 degrees (F). This will speed up the ich’s life cycle.
  2. Salting the tank by adding the recommended amount of salt dissolved in tank water.
  3. 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.

  • 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.

  •  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.

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.

  • 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.

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.

  • 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.

If you suspect your fish is sick and want to ensure you provide the right treatment, we recommend that you check out our best-selling and comprehensive book The Truth About Goldfish on Amazon today.

The Truth About Goldfish New Edition

It has entire chapters dedicated to in-depth diagnoses, treatment options, a treatment index, and a list of everything in our fishkeeping medicine cabinet, natural and commercial (and more!)

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!

  • 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.

  • 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?

  • 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.

  • 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.

  • 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.

  • 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.

Read more about Dropsy treatment here.


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.


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.

  • 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?

  • 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.

  • 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.

Related Read: What to Do About Tumors & Growths in Your Goldfish

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!

  • 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.

  • White, crusty lumps growing on (usually) the edge of the fins or even on the scales.
  •  “tumors” 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.


How to Troubleshoot a Sick Goldfish

Male hand holding PH tests in front of freshwater aquarium
Image Credit: M-Production, Shutterstock


Before you read any further:

Don’t assume that your goldfish has a disease once you find your fish’s symptom here.

Most of the time “sickness” is actually caused by poor tank conditions…

…which is why you should always test the water parameters first when you suspect a problem.

You can use a simple test kit to test all of the major parameters: pH, ammonia, nitrite, and nitrate.

Ammonia and nitrite should always read 0ppm. More than that, and your fish will start getting sick.

High nitrates (over 30ppm) can also cause issues as well.

The pH should also be in the right range (not far from 7.4) or it can cause issues with the slime coat, gills, and fins.

If your water tests fine, then and only then can you start assuming problems that require medications.

The key is to get to the root of the problem.

So without further ado… let’s dive right in!


Behavioral Symptoms

1. Gasping at the surface of the water (gulping air)

Gasping goldfish may hang at the surface of the water, appearing to “drink” the air. They also may suddenly dart up to the surface, take a quick gulp, then continue swimming. Gasping is an indication that something is not right in the tank – usually the water quality.

It may be that there is insufficient water agitation or tank space to provide enough oxygen for the goldfish to breathe, but most likely the nitrite, ammonia, or pH level is out of whack. Goldfish may also gasp at the surface when damage is done to the gills by store-bought medications or parasitic infestation.


2. Acting lethargic

Healthy goldfish are perky and move around most of the time – foraging around the bottom of the tank for food and exploring almost constantly. When a goldfish seems weak, sad, uninterested, or droopy, it is not well.

Lethargic goldfish may sit on the bottom of the tank or hang listlessly at the surface of the water. They show little concern when other goldfish start to nibble at them and generally seem depressed. If your goldfish seems lethargic or sickly, check the water. A pH crash or other irregular parameter change is probably occurring.

3. Jumping out of the tank

Sometimes incorrectly called “goldfish suicide,” goldfish jumping out of the tank is actually the goldfish’s way of trying to relieve the discomfort caused by poor water quality or parasites. Prior to jumping, many goldfish display erratic behavior by darting around frantically in the tank, scratching on objects, or twitching spasmodically. In all of their wild antics, the goldfish sometimes end up on the floor.

But water quality or disease may not always be the problem – sometimes the pursuit of male goldfish during breeding season results in females leaping from the tank trying to escape. If you have an aggressive goldfish that is bullying the others out of the tank, try separating the aggressive fish from the rest of the tank. If you find a goldfish that has jumped out of the tank, do not give up hope! Sometimes goldfish may revive when placed back in the water again if they did not dry out completely and it has been under an hour since they jumped.

The gills of the fish may be worked open gently by your fingernails if they have been dried shut. Tile or wood flooring underneath the tank provides a more likely survival chance for a jumper, as water taken out with the fish can keep it moist longer than carpet. Do not try to put a goldfish back in the water if the fish has concave eyes, gray eyes (from death), the skin cracks, or is not intact.


4. Sitting to the bottom of the tank

Goldfish that appear to be resting on the bottom of the tank are probably not enjoying a nice rest. Healthy goldfish remain active almost all of the time, and if your fish tank does not seem to have much life in it, it’s probably time to check into things.

Goldfish that sit on the bottom of the tank may lean to one side, clamp their fins, or show other signs of health issues. Goldfish bottom sitting with a red belly are usually beyond the point of recovery. Why do goldfish bottom sit? Usually, the problem is water quality, but sometimes the swim bladder may be the cause and it is simply a matter of constipation.

Constipated goldfish scoot along the bottom of the tank when startled, rather than muster up the strength to swim regularly as a goldfish affected by nitrite poisoning does. If the goldfish is constipated, try the frozen pea diet for a day or so until the fish regains proper swimming habits.

Read More: Goldfish Sitting at the Bottom of the Tank


5. Flashing (darting/scratching)

No, a flashing goldfish isn’t blinking out beams of light.  “Flashing” is when a goldfish suddenly dashes around wildly in the tank, sometimes rolling over on their side to rub on the substrate, careening into tank decorations, or hitting their faces in the corners of the tank walls. It may seem that your goldfish is having a fit.

Goldfish that flash are itching themselves, much like you do when you get a mosquito bite. Their movements seem uncontrolled and erratic. They are a signal that something is wrong. Flashing is a classic symptom of ich, but your goldfish may harbor almost any other pathogen instead. Any trace of ammonia, nitrite, chlorine, or a pH drop or spike can cause flashing as well.

6. Spasms/jerking

When severely irritated, goldfish jerk spasmodically. They may shake their heads suddenly from side to side, convulse their entire bodies, or flick their fins. Water quality problems are usually at the root of this symptom. Parasitic infestation can also cause major irritation.

7. Clamped fins

Any issue with water quality or nearly any parasite can cause goldfish to clamp their fins. These fish swim like they are in a straight jacket; all fins folded in closely to their body as they move. In some cases, the fins flick or twitch in an irritated manner.

Clamped fins, like flashing, are a sign of discomfort. Possible causes are measurable amounts of ammonia or nitrite in the water, but clamped fins often accompany parasitic infections as well. Symptoms of ich, flukes, fish lice, and velvet include clamped fins. Remember – always test the water before trying to identify a disease.


8. Rapid/labored breathing

Breathing problems are identifiable by observing the patterns of the gill movements. A goldfish breathing fast commonly are suffering from lack of oxygen.

If you are keeping your goldfish in a bowl (which is a big no-no; see Common Misconceptions), there is no water agitation and insufficient water volume for a goldfish to breathe. The fish will breathe hard in an effort to maintain sufficient oxygen levels. If this is the case, please move your goldfish into a larger tank as soon as possible.

Rapid breathing could also be a sign of stress, especially if it is accompanied by sitting at the bottom of the tank. Stress could be caused by being moved to a new habitat after a long ride in the car from the pet store. Breeding season sometimes heightens stress on female goldfish, which become exhausted after being chased around for hours by males.

But stress is also caused by poor water conditions or disease, so always check the water quality and, if there are no problems with it, gill flukes or nearly any other parasite may be the culprit. A goldfish experiencing difficulty breathing may frequently clear its gills by “yawning” repeatedly.

9. Swimming upside down

Does your goldfish seem to have difficulty balancing itself in the water? A goldfish that is stuck upside down is usually experiencing difficulty with its swim bladder – sometimes called “swim bladder disease” – the organ in the goldfish that controls its orientation in the water.

Intestinal impaction is usually the cause of goldfish flipping over. That means that meals may be too large or too frequent, or consist only of one dish (such as goldfish flakes, not the best choice for their diet requirements). Feeding dethawed frozen peas sometimes helps as a short-term fix. But buoyancy troubles are not always a symptom of swim bladder disorder, or flip-over disease as it is sometimes called.

High nitrites or the presence of ammonia in the tank water can cause goldfish to have problems swimming. A fish labored with internal parasites loses its appetite, and not eating causes the fish to float or flip over.

Read More: How to Treat Goldfish Swim Bladder Disease


10. Floating on side

If your goldfish is slightly tipping to one side, it may be normal behavior – especially if it doesn’t have a dorsal fin to help it balance in the water. You might also notice that the fish looks very thin. Water with high nitrites can cause this symptom.

11. Won’t eat (spitting)

Healthy goldfish consume everything edible they possibly can, leaving no remains. A fish that devours its food eagerly only to spew it back out again in a ground up cloud is showing signs of a problem. Stress can actually prohibit goldfish from swallowing their food, and this is common with fish that were just brought home from the store and need time to adjust to their new home.

A gill fluke infestation or mouth rot may also cause this symptom. Additionally, goldfish with internal fluid buildup (dropsy) are unable to swallow their food at advanced stages of the condition. If a goldfish becomes too sick even to eat, euthanasia is the most humane thing to do for the fish as starvation only would aid a slow death.

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Physical Symptoms (By Body Part)


12. Bulging eyes

If the eyes of the goldfish appear to have fluid-filled sacks surrounding one or both of them or protrude unnaturally, Pop-eye is probably the culprit (symptom of a bacterial infection). If the goldfish also has pine-coned scales (dropsy) along with bulging eyes, the condition is terminal and it would be best to euthanize the fish at this point. Stunted goldfish may sport permanent bulging eyes as a result of disproportionate growth.


13. Cloudy / whitish eyes

A goldfish with this symptom has eyes that look foggy like frosted glass. The fish may show difficulty in seeing food or bump into objects. This is called Cloudy-eye and is either the result of a bacterial infection that sets on after an injury, or the result of damage to the eye through some sort of burn; either from ammonia or the strong chemicals contained in some store bought medications.

14. Missing or damaged eyes

A goldfish will sometimes incur damage to the eye due to mishandling, running into a sharp tank decoration, injury from another fish in the tank, infection or chemical burns from water toxicity. In some cases, the eye may completely come off and leave the fish blind on that side. Telescope eye goldfish varieties are prone to eye loss or damage because of how far their eye stems protrude and their size.

Fortunately, most goldfish are able to heal on their own afterwards and can still live a happy life. With this in mind, it is important to choose tank decorations that are fish friendly and maintain good water conditions.


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15. Red gills

Though goldfish owners sometimes become concerned when they notice the red color inside their pet’s gills, this is not usually cause for concern. It is easier to see the red color inside of the gill covers especially on white or matte goldfish. If the gills are swollen or stuck open, however, gill flukes or a bacterial gill infection may be to blame. Gill flukes, like nearly every parasite, are treatable with salt.

16. Pale gills

As previously noted, healthy goldfish gills should be a vibrant red. Pale or whitish gills are a sign of illness. Parasitic infections such as gill flukes may cause microscopic bleeding of the gills, leading to a loss of color.

17. Holes in gill covers

This is a sign of a severe bacterial infection, which might benefit from antibiotic injections. But even after treatment, the holes won’t close.

Related Read: Curled-Gill Goldfish: Not a Breed But a Condition



18. Mouth stuck open

Sometimes a goldfish will get a piece of gravel lodged in its mouth while foraging for food at the bottom of the tank. The goldfish is usually able to work the gravel out on its own within a day, but during that time it will swim around with their mouth in the “out” position and look rather strange.

It is recommended to extract the gravel for your goldfish if 24 hours has passed with no improvement. Hold the goldfish gently in one hand with tweezers in the other. Press down underneath the chin slightly, then use the tweezers to remove the piece of gravel very delicately. In some situations, the goldfish’s mouth may be stuck open without any gravel in it. The mouth may snap back into place on its own, then return to the stuck position the next time the fish opens its mouth.

This is a more rare phenomenon, but it has been traced to stunting and disproportionate growth from being kept in too small of a tank for too long. The fish cannot eat and will face death through starvation unless humanely euthanized beforehand.


19. Mouth opening to one side only

This is actually not a symptom of a disease or problem with the water in the tank, but is actually a genetic defect that results in a small mouth sometimes angled to one side or even inverted. Goldfish with this condition may need to have their food served in smaller pieces than the other fish in the tank.

20. Red mouth

When the mouth shows redness and inflammation or even begins to cave in on itself, the goldfish is affected by mouth rot. The fish may rub its mouth on tank walls or decoration, causing further irritation. Blisters may also form. Mouth rot in goldfish can get very nasty very fast, so it requires immediate attention.

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21. Black spots/smudges

Either natural pigmentation changes may cause a goldfish to develop black on the scales, head or fins, or healing from a recent injury. As goldfish age, their color changes in sometimes unexpected ways. There is only cause for concern if the black marks come and go in a cycle, signalling a reoccurring problem with the tank water or a bullying companion.

Ammonia burns after a spike will heal black, but usually revert to the original color of the fish with time if water conditions remain relatively stable. Fins healing after a case of fin rot sometimes show black edges.

Read More: Is Your Goldfish Turning Black?


22. White spots

If your goldfish appears to be dusted with snowflakes or grains of sand, ich is probably the culprit. The protozoan is white like a speck of lint and will multiply until both the fins and body of the goldfish are completely sprinkled. Sometimes a single speck of ich may come and go, affixing itself to the tail or the wen of a goldfish when the fish has a compromised immune system.

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23. Raised lumps

Abnormal lumps underneath the skin or attached to the scales are tumors, which may be cancerous or not. Tumors come in all shapes, sizes and colors and can get rather huge when left untreated. Tumors may manifest themselves as a white lump, pink lump, brown lump or dark lump. These masses may even show up on fins as a result of toxins building up in the water. Tumors are removable, but if they are left untreated the fish may die.

24. Red spot(s) on body

These are usually ulcers, or the beginnings of them. Ulcers start out as a tiny red patch of blood on the skin, then progress until the skin begins swelling and eroding. However, red spots on the body may be bites from a parasitic infection such as anchor worm or fish lice, so examine the fish closely.

25. White, milky film on body

This is actually hyperactivity of the goldfish slime coat, producing excess mucus in response to the threat of parasites or poor environmental conditions. Check the pH for fluctuation and test the water for the presence of ammonia or nitrite. If the water is fine, parasitic attack is probably the cause. Skin flukes, anchor worm and cause goldfish to produce a milky coating on the skin.

26. Pale color

When a goldfish has lost its color, is usually a signal that the fish is not well and is suffering from either poor water quality or disease.

If nitrites are detectable in the water using a water test kit, you have probably found the cause of color loss and should take action to reduce them. Change 50% of the water immediately if ammonia or nitrite levels show up, or if the pH has suddenly shifted.

Stress can also cause a lack of bright color in goldfish for a period of time until they adjust or the cause of the stress is removed, such as an aggressive tank mate. Goldfish may change their color from vibrant to dull while their immune system is battling disease, such as a parasitic attack. Any number of parasites can cause color vibrancy to go away.

To ensure that your goldfish show the most coloring, provide a high quality diet, which helps to enhance coloring. Also, ensure that the tank gets enough light during the day hours (but not too much – you don’t want an algae explosion!). This will help to maintain good coloring in goldfish.

27. Sores

Red, painful-looking and sometimes large sores on the body of a goldfish are ulcers. Ulcers are caused by bacteria that attack the skin when the fish’s immune system is suppressed, usually by poor water quality. Ulcers continue to eat away at the skin of the goldfish until the fish can take no more and finally dies.


28. Fluffy Patches

This may be a sign of a fungal or bacterial infection causing cotton-like growths. Patches of fuzz on the head, body or even fins might be tricky to identify unless you have a microscope.

29. Worms sticking out of body

These are anchor worms – a parasite that attacks goldfish during certain times of the year. Anchor worms are treatable if caught soon enough.

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30. Red belly

A goldfish with a red belly is almost always suffering from nitrite poisoning. The effects of poor water quality, at advanced stages, can cause internal bleeding and death. Goldfish that display a red belly are at an advanced stage of poisoning and postponement of euthanasia only prolongs their slow death. Immediately change the water to save any other fish in the tank.

31. Swollen belly (bulging abdomen)

If the scales of the goldfish are not raised but the abdomen of the goldfish is bulging unnaturally, egg impaction is the likely cause. A female goldfish with impacted eggs is more and more susceptible to bacterial infection with time. The only way to save the fish at this stage would be to use a hand-spawning-like method to release the eggs.

Male goldfish or females that are not mature enough to bear eggs may have a kidney or liver disorder, only fixable through surgery. But remember that an overfed goldfish’s stomach will also distend beyond its normal size, which is why overfeeding is never a good idea.


32. Sunken belly (abnormally thin / wasting away)

A goldfish with a sunken belly is usually experiencing the harmful effects of ammonia accumulation in the tank. This can cause the fish to be susceptible to bacterial infection, which makes the stomach appear concave. If the water is fine, an attack of goldfish flukes or another parasite may be causing the goldfish to lose its valuable nutrients. A sunken belly may also be a sign of an underfed goldfish.

33. Bent/kinked back

This is scoliosis in fish, a condition caused by either genetics or electrocution. Scoliosis may cause the scales to pinecone at the curve of the spine. Scoliosis has no cure in fish.

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34. Scales sticking out all over (pineconing)

This is dropsy, a condition where the buildup of fluids in the goldfish causes the body to swell in such a way as to make the scales stand out and prickle. Dropsy itself is not a disease; it is an indication that something is wrong with the water quality or with the internal organs of the fish. Dropsy, when combined with bulging eyes, is terminal.


35. Scales peeling

When the scales of the goldfish in an area or a patch seem to have peeled back, leaving a bare place on the goldfish’s body, that is a burn. Burns from fluctuating pH levels may occur at any time while the tank is still cycling and trying to establish a colony of beneficial bacteria.

36. Scales coming off / missing

When a goldfish has missing scales, there is a distinct area on the body of a metallic scaled goldfish that reflects no light and can appear darker than the rest of the scales. A goldfish can lose anywhere from one scale to many, depending on the severity of the problem.

Goldfish that have many missing scales are actually showing a symptom of a symptom; the scales are being knocked off the goldfish as a result of flashing. If the problem gets resolved (either fixing the water quality or eliminating the presence of parasites), the scales should grow back with time. If the goldfish is a Pearlscale, however, the missing scales will not resemble pearls but regular scales when they grow back.

Please note that a goldfish may also lose a scale or two when trying to squeeze through the opening of a decoration in the tank that is too small to fit through.


Tail & Fins

37. Bloody streaks / red spots in tail or fins

This is a sure sign of a serious problem with the water. High ammonia or nitrites can cause blood hemorrhaging (broken blood vessels) of the veins in the tail of the goldfish, resulting in thin red lines or spots of blood appearing in the fins. Water changes and proper room in the tank can help ensure recovery.


38. Shredded or frayed tail or fins

Traceable ammonia or nitrite levels in the tank can cause the fins of a goldfish to shred and fray like someone has snipped the goldfish’s fins over and over with a pair of scissors until the ribs of the fins give the fish a spiky appearance. Fin rot, too, will cause the fins to fray and disintegrate. The parasite Hexamita, a protozoan brought on by poor environmental conditions, can cause this condition also.

39. Tears/splits in tail or fins

If there are multiple goldfish in the tank, sometimes aggression may occur and leave the victimized fish with splits in the fins. The bully may grab a goldfish’s tail in his mouth and tear savagely, causing rips to ensue. Additionally, poor water quality may cause splits to appear in the tail. Frayed fins may be a sign of fin rot.


40. Milky film on tail or fins

This is caused by excess mucus production in response to poor environmental conditions or parasitic attack. Milky skin is easily detected on varieties such as the Black Moor goldfish.

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41. Floating poop/air bubbles in poop

The diet of the goldfish is not varied enough, and air bubbles from meals upon meals of dry flakes are accumulating in the fish’s digestive track and expelled in the casts. Healthy goldfish stool should be the color of the goldfish’s food, usually dark brown in color, and sink to the bottom.

42. Long, trailing white poop

Hollow, stringy poop is the outer casing of the stool. They are called casts, and are normal in goldfish that are kept with sand as the substrate. However, if the poop is long and trailing, this indicates an internal issue such as intestinal bacterial infection or a poor diet. (Sorry for the following picture…)


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“How Can I Use This Information For My Fish?”

So now you know what your goldfish’s symptoms are from.

What should you do?

Lucky for you, we created just the thing to help you nurse your goldfish back to health and keep it from falling sick again.

You’ll also learn the 5 critical mistakes most people make in your situation – and how to get things back on track fast.

It’s all in our eBook called “The Truth About Goldfish.”

Join the Fastest Growing Goldfish Facebook Group to Post Your Question

I’ve got to say I was blown away by the number of comments this article has gotten.

Since so many people need help, I decided to start a free private goldfish Facebook group as my way to say thanks to my awesome readers.

It’s a great place for people who are struggling with sick fish to get advice from fellow hobbyists and post photos (something the comments section on here can’t do).

There are so many great members willing to dedicate their time to helping others…

So, what are you waiting for?

Head over to the group now. I look forward to seeing you there!

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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.

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