Goldfish Diseases: Diagnosis and treatment

Cartoon of a sick goldfish with spotsIf you’ve spotted something unusual about your goldfish and think it may have a disease, if you know your fish definitely does have a disease and you’re wondering how to treat it, or if you just want to learn about goldfish diseases and how to avoid them, then you’ve come to the right place!

In the articles below, we look at common goldfish diseases – including white spot (also known as ich), fin rot, pop eye, dropsy, swim bladder disease and more – and explain the symptoms of each disease, the cause of each disease and – most importantly – how to treat each disease.

White Spot (Ich)

Have you noticed white spots on your goldfish? Does it look like grains of salt or sugar have been sprinkled on to your goldfish’s body, fins or gills?

If the answer is yes then your fish may be infected with “white spot disease”, also known as “Ich” or “Ick”.

Read this article to Find out more about what white spot disease is, what causes it and how to treat it…

Pop Eye

Pop eye, which is also sometimes known as “exophthalmia” isn’t strictly a disease in and of itself, but rather, it is the result of another underlying issue or infection. It causes one or both of the eyes of the goldfish to protrude from the socket to some degree, ranging from a slight bulge to quite pronounced, depending on the severity of the condition.

Read this article to find out more about pop eye in goldfish…

Swim Bladder disease

Although often called a “disease”, swim bladder problems are actually a symptom or disorder affecting the goldfish’s swim bladder that can have a number of different causes. There is not one specific “disease”  that is the cause of all swim bladder problems in goldfish!

Read this article to find out what causes swim bladder problems in goldfish and how to treat them…


Dropsy is a very serious condition affecting goldfish. If you notice your goldfish looking fat, swollen or “about to explode” then the problem is probably dropsy.

Read this article to find out more about the symptoms of dropsy, what causes dropsy and how to treat it.

Fin Rot

Fin rot isn’t a disease in itself, but rather a symptom of disease or infection.

If your goldfish has fin rot then you will notice their fins start to appear frayed or ragged, as if they’ve been torn.

Read this article to find out what causes fin rot in goldfish and how to avoid and treat fin rot…

Congested Fins

Congested fins can often be confused with fin rot (see above), as the symptoms are very similar.

But what are congested fins? What causes congested fins in goldfish? And how do you treat a fish that is suffering from congested fins?

Read this article to find out everything you need to know.

Turning Black

While your goldfish turning black in places isn’t necessarily a health issue, it can often be a sign of serious problems in your tank.

Black spots or smudges should not just be considered normal and it is important to do what you can to find out what is causing your goldfish to turn black.

Read this article to learn more and find out what to do if your goldfish develops black smudges or spots.

Lice & Worms

Lice and worms are common goldfish tank parasites. Both lice and worms can lead to health problems in your fish and should therefore be dealt with as soon as a potential issue arises.

Read this article to find out how to spot lice and worms on your fish and how to rid your tank of these parasites…

Cotton Mouth

Cotton mouth is correctly called “Columnaris bacterial,” and as the name suggests, it is a bacterial infection. However, due to the unique appearance of cotton mouth, it is often wrongly diagnosed as a fungus, leading to ineffective treatment.

Read this article to find out about cotton mouth in goldfish and how to treat this bacterial infection.


Flukes in goldfish doesn’t refer to an actual disease, but rather a parasite, which comes in two different varieties depending on whether it affects the body or the gills of the fish.

Read this article to learn about flukes and what to do when these parasites infest your fish tank.


Velvet in goldfish is caused by the presence of a parasite called “dinoflagellate,” and causes the scales and body of the fish to take on a rough, dusty and slimy look that vaguely resembles the texture of velvet fabric.

Read this article to  to learn more about velvet, how it is caused, and how to treat it.

Hole in the Head

Hole in the head begins with a small sore, or multiple sores, on the head of your goldfish. These sores usually appear around the eyes and grow progressively larger over time, eventually penetrating the outer layer of skin.

Read this article to identify the symptoms of hole in the head disease and learn what to do if you spot hole in the head in your goldfish.


Ulcers are open sores on the surface of the body of the goldfish, which look like red, white or pink wounds. Ulcer sores are caused by the presence of bad bacteria attacking the surface of the scales, leading to inflammation, irritation and infection.

Read this article to learn more about ulcers in goldfish, what causes them and how to treat them.


Constipation is one of the most common problems that goldfish face. So, if you’re wondering how to tell if your goldfish is constipated – and what you should do about it if so – then read on to find out!

Read this article to learn more about constipation in goldfish.

Fish Pox (Carp Pox)

Fish pox, also known as carp pox, most commonly affects domestically kept koi carp.

However, goldfish and many other species of fish are also prone to contracting the condition, particularly if they are kept together with koi carp in ponds.

Read this article to find out all about pox in goldfish.

Goldfish & Leeches

Leeches are not among the most common of goldfish parasites, but nevertheless, they are rather nasty, and easily introduced into an existing tank.

Read this article to find out how leeches could get into your tank or pond and how to remove them if they do.

Goldfish & Costia

Costia is a tiny parasite that may live on your goldfish and within the water of the tank for some time before it causes any problems. A goldfish with costia will develop slimy-looking patches over their gills and heads, and will tend to clamp their fins down close to their bodies.

Read this article to find out how to identify and treat costia in your fish.

4 thoughts on “Goldfish Diseases: Diagnosis and treatment”

  1. I’ve got two black goldfish with a very film and grey spots. Methal blue cures it but I don’t know what it is

  2. I have a goldfish with purple dots. How can I fix that problem? But he looks fine to me other than that. He is moving fine, breathing is fine and he is not at the bottom of the tank that much either.

  3. So one of my goldfish has a lot of pink things all around it’s body and a lot of it on its fins.Please let me know if there is a cure to do this.


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