Common Goldfish Diseases – Causes, Symptoms and Treatments

Let’s face it. You cannot stop your goldfish from falling sick. But, of course, you can make them less susceptible to diseases.  To that end, your first step should be knowing more about goldfish diseases, their symptoms, causes, and treatment methods.

In fact, there are many different types of goldfish diseases. And identifying signs of a sick goldfish could be challenging! For instance, just because your fish is breathing fast or gasping doesn’t necessarily mean it is sick. Even a healthy goldfish can show similar symptoms due to poor tank conditions.

So, is your goldfish showing any signs of illness? Maybe you know your fish is sick but not sure how to treat it. Or perhaps, you are simply curious about the common causes and symptoms of goldfish diseases. In any case, this comprehensive guide on goldfish diseases aims to address all your concerns, questions or confusion.

How to tell if your goldfish are actually sick

Of course, a sick fish will behave abnormally. In addition, it may manifest some physical symptoms on its body parts. However, before you apply medicines to the fish, make sure it is actually sick. Sometimes, you can confuse the symptoms of poor water conditions with the symptoms of a goldfish disease. So, how do you know if your goldfish is actually sick? Unfortunately, there is no clear answer to that question. However, testing the water and closely observing your fish could help you make an informed decision. For instance, if you suspect poor water quality is the culprit, consider testing the water for ammonia and nitrite levels.

When do goldfish die from diseases?

In theory, most goldfish diseases are completely curable. The sad reality, however, is that goldfish dying from an illness is a common phenomenon. So, if you are not sure why your goldfish died, consider taking a closer look at the symptoms. For instance, if the dead fish has white or black spots on its fins, maybe the reason for its early demise is a disease called ich. However, diseases are just one of the reasons why goldfish die. In fact, your goldfish can also die from overfeeding, poor water quality, unfavorable tank conditions, injuries, stress and old age.

Don’t confuse any unusual characteristics with a goldfish disease!

Some goldfish types come with unusual characteristics. For instance, an oranda goldfish often has a small lump on its head. So, it is easy for you to confuse that lump with a tumor. However, know that the head-growth is a common characteristic in an oranda goldfish. Likewise, you can confuse the enlarged nasal septum of a pompom goldfish with signs of fungal infections. A bubble-eye goldfish, on the other hand, comes with eye-bubbles, which you can easily mistake for an infection. So, before you assume your goldfish has a disease, make sure you know what goldfish type you are raising and if they have any unusual characteristics.

What types of diseases do goldfish usually suffer from?

Usually, goldfish are susceptible to a few different types of diseases, such as parasitic diseases, bacterial diseases and fungal infections. For instance, parasites like flukes, ich, velvet, and fish louse, if not treated early, could often result in a deadly goldfish disease. On the other hand, your goldfish are also vulnerable to bacterial infections, such as fin rot and mouth rot. Often, if your goldfish has open wounds, it could also get fungal infections. Typically, a goldfish with fungal infections will have whitish furry growths on its skin, gills or fins. By now you must have a lot of questions about the different types of goldfish diseases. So, let’s take a close look at some common goldfish diseases.

1. Goldfish Fin Rot

Simply put, fin rot is rotting of the goldfish fins. In fact, fin rot, AKA tail rot, is a symptom of bacterial infection in the fins. Usually, stressed or injured fish are more susceptible to this type of infection. Importantly, if you notice any symptoms of fin rot, you should start the treatment as soon as possible. Otherwise, the symptoms could get worse.

Fin rot symptoms

Typically, the early signs of fin rot include ragged or frayed fins with a red or white edge. Gradually, the white edge will spread downwards to the base of the fins. In fact, if left untreated for long, the fins could appear torn or broken. Often, you can also notice red streaks on the fins. Also, if your goldfish has fin rot, it would rub the infected area against the tank wall or substrates.

What causes goldfish fin rot?

Often, poor water quality is one of the main reasons. In fact, the quality of your tank water deteriorates when ‘bad’ bacteria outnumber ‘good’ bacteria in the water. As a result, the immune system of your goldfish weakens, making them more vulnerable to bacterial infections like fin rot or mouth rot. Of course, there are other direct causes but poor water quality often aggravates the problem. More specifically, some direct causes of goldfish fin rot include an injury due to fin nipping or fighting with other fish, overcrowding and low water temperature. 

Fin rot treatment and prevention

First of all, start by testing the water. In particular, test the ammonia level and pH level of your tank water. Ideally, the ammonia level should be at zero, while the pH value should not cross eight. In addition, you may also want to test the nitrite and nitrate levels of your tank water. Typically, it is safe to keep the nitrate levels anywhere between zero and 40 ppm. So, if you notice any spikes in ammonia or pH or nitrate levels, consider treating the tank water.

For water treatment, add one tablespoon of aquarium salt or pure sea salt per 10 gallons of water. Once added, keep your goldfish there for at least five days. However, if you still don’t see any improvement, consider seeking advice from professionals. In general, if you notice the white areas turning black, that’s actually a sign of improvement. If nothing works, your vet may prescribe antibiotics.

Since it is easier to prevent than treat, you should begin the treatment as early as possible. Remember, it is almost impossible to cure fin rot once it spreads to the fin base.

For prevention, consider performing partial water changes every week. Ideally, changing around 25% of the tank water should suffice. In addition, clean the tank filters and substrates regularly. Most importantly, don’t make your tank overcrowded. Ideally, one fish per 10 gallons of water is a good rule of thumb.

2. Ich or White Spot Disease

Ich is a type of parasite infection that often attacks a stressed or weakened goldfish. Usually, ich will find a way into your aquarium via a new goldfish or tank equipment. So, make sure you always quarantine a new fish for a few days before introducing it to your goldfish aquarium.

Ich symptoms

Almost always, an ich-affected goldfish will have white spots on its body. Often, the white spots look like small grains of salt covering the pet from its head through the tail. In addition, the fish could have breathing difficulty, loss of appetite, and an urge to rub the affected areas against the aquarium wall.

What causes Ich?

As with most parasites, ich remains invisible in the initial stage of its lifecycle. Hence, spotting an ich-affected fish or object is almost impossible in the beginning. In fact, you’ll not see the signs of white spot disease until the parasites would enter the last phase of their feeding cycle. After that, they will get separated from the fish but will give birth to more parasites. Eventually, all the fish in your aquarium could get affected. So, what are the root causes of ich? Typically, ich attacks any fish that have a weak immune system. For instance, poor water quality could lower the immunity of your fish, making it susceptible to white spot disease or ich.

Ich treatment and prevention

Typically, you can cure the white spot disease by adding salt to the tank water. However, if you delay the treatment, the situation could get worse. In fact, ich can even kill your fish, if left untreated for a long time. But don’t worry! Most conditions are curable if you take the below steps.

Firstly, test the tank water. If you notice unusual spikes in ammonia, pH and nitrate levels, go for a 25% water change prior to starting the treatment.

Secondly, heat up the tank water to around 75 degrees (F). That way, you will accelerate the lifecycle of the parasites.

Thirdly, add salt to the tank water. Ideally, adding one teaspoon of salt per three gallons of water should suffice.

Finally, continue the treatment for at least two weeks. If you don’t see any improvements, consider using commercial treatments.

Also, it is important to continue the treatment for at least five days after complete healing. That way, you can avoid any relapse of the disease in future.

3. Swim Bladder Disease

First of all, know that the term ‘swim bladder disease’ is a bit of a misnomer. Often, you’ll see rampant use of the term to refer to any floating issues in a fish. In truth, swim bladder disease means that the fish’s swim bladder is not functioning properly. So, what does the swim bladder do? Put simply, it is a gas-filled organ that helps your goldfish to stay afloat in the water. For some reason, if the swim bladder gets compressed or deformed, your fish will experience buoyancy problems. Thankfully, there are ways to treat swim bladder disease.

Symptoms of swim bladder disease

Mostly, a goldfish with swim bladder disorder will have some kind of floating problems. For instance, the troubled fish might swim sideways or upside down. Also, your fish may have difficulty swimming from the bottom to the top of the tank or vice versa. In addition, a goldfish with swim bladder disorder could look a little inflamed or enlarged.

Causes of swim bladder disease

Often, goldfish get this disease as a result of swim bladder compression. In fact, there are a few different ways your pet’s swim bladder could get compressed. For instance, if you overfeed your goldfish, the additional food could put increased pressure on its swim bladder. Likewise, some other causes of swim bladder disease could be poor food quality resulting in constipation and abdominal bloating, lack of fiber elements in the diet. Also, feeding them dry pellets means that the pellets would later soak in water and expand inside the intestinal tract. In addition, poor water quality may cause bacterial infections in the swim bladder, resulting in inflammation of the bladder.

Treatment for swim bladder disease

First things first, test the tank water and take the necessary steps to improve the tank environment. Secondly, if you think overeating is the cause, stop feeding your fish for at least three days. After three days, consider feeding them foods that are low in protein. For instance, you can give them frozen peas without the skin. Eventually, this should help cure swim bladder disorder. However, if the problem persists, it could be due to bacterial infections in the bladder. In that case, consider seeking professional treatment.

4. Black Smudge

Often, black smudge or black spots are symptoms of some underlying health problems in your goldfish. However, that doesn’t mean your goldfish cannot turn black naturally! In fact, some goldfish breeds naturally come with black and white colors. Nevertheless, it is very rare for a goldfish to turn black from other colors.

Black smudge symptoms

Typically, symptoms of black smudge disease include sudden development of black spots on certain areas of the fish’s scales, fins or tail. In some cases, the black spots could spread to other areas, such as the head and gill plates of your goldfish.

What causes black smudge?

Mostly, goldfish get black smudge from chemical burns. Often, high ammonia levels in the tank water would burn the fish skin, resulting in black spots on the burnt areas. Perhaps, you already know that goldfish don’t have a stomach and they poop a lot. So, the feces of your goldfish often build up at the bottom of your tank, creating the toxic ammonia chemicals. Hence, it is important to keep the tank clean by removing the feces at frequent intervals. Ideally, you should do partial water changes to keep the ammonia levels in check. In addition, black smudge can also be caused by parasite infections.

Treatment for black smudge

Ideally, the treatment process should start with the identification of the root cause of the problem. For instance, if a high ammonia level is the culprit, your treatment should start with testing the ammonia levels in your tank water. If you notice any ammonia spikes, consider performing partial water changes. Often, if the ammonia level is very high, you should change 50% of the tank water. Meanwhile, avoid overfeeding your fish to eliminate or limit any ammonia buildups. In addition, consider adding carbon to the aquarium filter. That way, you can negate the toxicity of the water to some extent. On the other hand, if parasite infection is the culprit, then consider resorting to professional medical advice for faster recovery.

5. Anchor Worm (Lernaea)

Interestingly, anchor worms are not a worm. Actually, they are a kind of parasite that would cling to the skin of your fishy pet.  Thankfully, they are macroscopic. So, you should be able to see them in plain sight. Still, you may fail to notice them unless you pay close attention. Often, anchor worms would go noticed until severe damages have been done to your fish. More alarmingly, these parasites are contagious, meaning that more fish in your tank could get affected, if not treated early. Anchor worms become harmful to your fish after mating. At this stage, the female parasite burrows into the flesh of your fish, causing serious damage to it.

Symptoms of Anchor Worm

Often, the initial signs are too subtle to notice. At the early stage, your only clue is behavioral symptoms. For instance, if you notice your fish rubbing its body against the tank wall, it is perhaps a symptom of anchor worm disease. Next, look closely and you might notice a worm-like parasite hanging from your fish’s scale. Usually, the parasite would bury its head into your fish’s skin, with the rest of its body sticking out from there. Typically, the visible portion of the parasite’s body looks like loose ends of a whitish green thread. Meanwhile, your goldfish may experience other symptoms, such as redness and inflammation the affected area, breathing difficulty and low energy.

What causes Anchor Worm disease?

Often, anchor worm parasites come from an outside source. For instance, anchor worms can enter your tank water with a new fish or recently added live plants. Hence, you should always quarantine a new fish or live plant before introducing it to the tank.

Anchor Worm treatment and prevention

First of all, you need to add salt to the tank water. That way, you can reduce the risk of any secondary bacterial infections in your goldfish. In general, adding two tablespoons of aquarium salt per five gallons of water should suffice. At this stage, you can start pulling out the parasites manually using tweezers. However, manual removal of the parasite needs to be done with careful attention. Often, pulling out a deeply attached parasite could do more harm than good to your fish. So, it is always a good idea to use sedatives to your fish before performing the manual removal process.

Once you have removed all visible parasites, consider applying medications to the fish’s wounded areas. You’ll also find some anti-anchor worm medicines for quick results. Finally, for prevention, consider cleaning the aquarium. Also, consider performing a partial water change to get rid of the excess salt from the water.

6. Dropsy 

Technically, dropsy is not a disease but a symptom of an underlying health condition. Often, the symptoms of dropsy hint at a kidney malfunction or bacterial infection. Long story short, dropsy generally means your goldfish has lost its natural ability to release water from their bodies. Consequently, your fish swells up to a point where its belly is seemingly on the cusp of an explosion. Sadly, most cases of dropsy are incurable. However, early detection of the symptoms might give a chance to at least try for a complete cure.

Dropsy symptoms

As mentioned, an abnormally swollen belly is a telltale sign of dropsy. In addition, watch out for symptoms like protruding eyes, and chronic fatigue or loss of appetite. At a later stage, you may also notice raised scales on your fish’s body. In fact, the raised scales often make the fish look like a pine cone. In some cases, the fish could also experience buoyancy problems. For instance, if you notice your fish floating at the top or sinking to the bottom of your tank water, be wary. Granted, this could be a symptom of swim bladder disease but you never know!

What causes dropsy?

Put simply, dropsy happens when your goldfish loses its natural ability to maintain the right water-salt ratio necessary for homeostasis. Normally, the fish relies on its kidney to release any excess water from its body. However, if for some reason, the kidney malfunctions, your fish’s belly would swell up like a balloon. So, why does the kidney malfunction? Often, the reason of the malfunction is a bacterial infection. Suffice to say, the root causes often boil down to poor water quality, bad tank conditions and bad diet. However, you may often find it difficult to identify the actual cause of dropsy. For instance, maybe your fish is soaking in the excess water through an injury in its body.

Dropsy treatment and prevention

Unfortunately, most treatment options for dropsy are futile. In fact, early detection of symptoms is the only way to save your fish. Sadly, however, most symptoms of dropsy become visible very late. Often, by the time you’d know your fish has got dropsy, it’s already too late to cure the disease completely. So, should you simply sit back and let it die? Of course not! Instead, take the below steps.

First of all, place the sick fish into a quarantine tank. That way, you are securing the other healthy fish away from any unnecessary treatments.

Start the treatment by adding around one tablespoon of salt to the quarantine tank. Importantly, you should use Epsom salt instead of any aquarium salt. Epsom salt contains magnesium sulfate, which helps extract the surplus water from the fish’s body.

Next, consider setting the water temperature at around 75 degrees Fahrenheit. Finally, add antibiotics to the water. This should help cure any bacterial infections.

The sad reality is that most fish with dropsy would eventually die. So, it is always a good idea to prevent the disease. For prevention, consider keeping the tank water clean. Also, test the water and conduct partial water changes at frequent intervals.

7. Goldfish Eye Diseases: Pop Eye and Cloudy Eye

Some goldfish come with naturally big eyes, but for most others – it’s a sign of eye disease. Case in point, pop eye is a common condition where one or both eyes of the fish would protrude. Even worse, the popped eyes could fall out as a result of excessive swelling of the eye bags. On the other hand, some goldfish experience cloudy vision as a result of a condition called (you guessed it!) cloudy eye. In this case, your fish would have difficulty seeing an object clearly. As an aside, both pop eye and cloudy eye could be a symptom of other goldfish diseases, such as dropsy and tuberculosis.


Often, the symptoms come gradually. For instance, the initial symptoms of pop eye could be slight swelling of the eye or eyes. With time, the symptoms would worsen to a point where your fish’s eye bags would protrude outwards from its head. Later, you could see red marks or rupture in the affected eye. On the other hand, symptoms of cloudy eye disease include a foggy iris and vision difficulty.


Typically, pop eye occurs when your fish has an internal bacterial infection. Eventually, this could result in a fluid buildup at the back of the fish’s eyeballs. Often, poor quality water is the reason for pop eye. However, if you see only one eye of the fish has been affected; it is probably not because of poor water quality. For instance, an injury at the time of a fight with another fish could also cause pop eye. Cloudy eye, on the other hand, could be caused by eye flukes, tuberculosis, ich, eye injury and bacterial infections.

Treatment options

Ideally, any treatments for goldfish eye diseases should start with identifying the root cause of the problem. For instance, if poor water quality is the cause, then a thorough water treatment is the solution. Often, this might include performing partial water changes, lowering ammonia levels and nitrate levels of the water. Likewise, adding salt to the tank water is a good way to heal any physical injury in the fish’s eyes. On the other hand, antibiotics often come in handy to cure any internal bacterial infections. In any case, early treatment is advisable for a quick recovery. Remember, delay in treatments may result in complete vision loss for your beloved pet.

8. Hole-in-the-Head Disease

Granted, the name sounds scary but that’s what it is. Usually, the hole-in-the-heart disease would start off as a small red spot on the fish’s head, adjacent to its eyes. Gradually, the sore would burrow into the fish’s skin, eventually making several big holes in the fish’s head. As you can imagine, this disease can kill your fish, if not treated early.

Symptoms of hole-in-the-heart disease

Typically, the disease spreads gradually and manifests different symptoms at different stages of its lifecycle. As mentioned, it begins with a small red sore but gradually grows larger and culminates in multiple deep holes on the head of the affected fish. Some other symptoms include holes in the fin base and visible mucus on the slime coat. Often, the affected fish would look paler than usual.

What causes hole in the head?

Honestly, researchers are still not sure about the root cause of this disease. In fact, one school of thought says parasite and bacterial infections are the culprit. Conversely, some recent studies blame it entirely on poor tank conditions. In either case, it is evident that poor water quality, stress and other environmental factors play a major role in making goldfish susceptible to this disease. In addition, other causes may include improper aquarium lighting, bad diet, and a lack of a proper system for temperature regulation.

Treatment for hole in the head

First of all, check if your goldfish tank is overcrowded. In that case, your first job is to buy a new tank and transfer some fish to that tank. Next, test the water for ammonia and nitrate levels. Actually, if your goldfish has symptoms of hole-in-the-head, chances are your water quality is extremely bad. So, take the necessary steps to fix your water quality issues. For instance, you may need to change the water, remove any uneaten foods and the fish’s feces from the bottom of your tank.

Also, before you start treating the sick fish, move it to a separate tank. Next, add salt to the water. Ideally, one tablespoon of salt per five gallons of water is enough. In addition, consider using medicines, such as, antibiotics. Meanwhile, fix any tank lighting issues and keep the temperature at around 75 degrees Fahrenheit. Finally, make sure you feed your goldfish a balanced diet.

By now you should have good knowledge and understanding of common goldfish diseases. However, knowledge means nothing until you take action. Ultimately, you want to keep your goldfish aquarium disease-free. To that end, consider taking preventive measures to keep your aquarium environment clean and healthy.