Goldfish Diseases and Their Symptoms

Woman playfully holding a stethoscope to her goldfish bowl

Goldfish are fairly hardy fish, and most will live for a long time if they are cared for properly. Even if you look after your pet like it's the most precious thing in the world, knowing goldfish diseases by symptoms will help to ensure your fish gets the right treatment before its too late.

Goldfish Disease by Symptoms

Anchor Worm

Anchor worm is a parasite that is most commonly found in fish that are kept outside in ponds, like koi and other large goldfish. Anchor worm is not really a worm but rather it is the feeding stage of a copepod called Lernae. After mating, the female anchor worm burrows into the flesh of the goldfish and eventually transforms into a wormlike form. A part of the worm usually sticks out from the fish's body, resembling a reddish thread. It is usually found near the fins. An infected fish may shake its head vigorously to try and rid itself of the parasite. If left untreated, anchor worm eventually destroys the gill and muscle tissue around the affected area.

Fin Rot

Fin rot is caused by a number of things, from injury to disease. It can also be the result of either a primary or secondary infection. If the tail fin is very ragged looking, the fin rot is normally the result of a bacterial infection. On the other hand, if the tail is rotting away evenly, then it is the sign of a fungal infection. If the fin takes on a whitish margin, a bacterial infection has taken hold and if left untreated, it will eventually enter the body of the fish. As long as the fish is treated before the infection reaches its body, the tail fin will grow back.


Ich (ick), sometimes called white spot disease, appears as white spots on the side of the fish. These spots are about the size of grains of salt, and they are actually parasites called Ichthyophthirius multifiliis. Ich is fast spreading and very lethal to goldfish if left untreated.

Velvet Disease

Velvet disease is caused by a parasite called Oodinium, and it results in a golden, velvet-like coating all over the fish's body. It is often difficult to identify in goldfish because the coating is almost the same color as the fish.


Dropsy is one of the rarer goldfish diseases. While treatments are available, a full recovery is virtually impossible. Signs of dropsy include bloated eyes, a swollen body and protruding scales. This condition is usually a result of organ failure due to cancer or extremely poor environmental conditions.

Fish Lice

Fish lice is very rare, especially in goldfish, but that doesn't mean it doesn't still happen. Signs of fish lice include disc-shaped parasites noticeable on the skin of the fish and ulcers on the body of the fish.

Black Spot Disease

Black spot disease isn't really a disease but rather a natural reaction by the goldfish when their water has too high a concentration of ammonia. When this happens, black spots will form along the side or near the back side of the fish. This usually happens most often with goldfish and koi kept outside.


Chilodonella is difficult to determine in goldfish because the disease has very few visible signs during the initial stages. In most cases, by the time the disease is detected, severe tissue damage has already occurred. Typical symptoms of chilodonella include clamped fins, lethargy, difficulty breathing and loss of appetite.

Hole in the Head Disease

Hole in the head disease will usually start off as small sores on the head, usually around the eyes. Eventually, these sores erupt into tubular formations filled with cream-colored mucous.

Pop Eye

Pop eye is a condition that's typically caused either by parasites or very poor water conditions. The symptoms of pop eye include very inflamed eye sockets, protruding eyes and in some cases, a hazy film over the eyes.

Slime Disease

Slime disease is usually a result of another disease like chilodonella or parasites. Its symptoms include a grayish coating on the fins or body. The goldfish will also look as if it is trying to scratch itself against the tank or other objects inside the tank.


Flukes are microscopic parasites that embed themselves in the gills of the goldfish and cause them to become red and swollen. The fish will also spend more time near the surface of the water because it will have difficulty breathing as a result of this disease.

Treating Goldfish

When treating goldfish disease by symptoms, cleaning and sanitizing the tank is one of the most important things you can do. Remove the affected goldfish and put it in an isolation tank. Thoroughly clean and sanitize the tank and refill it with fresh, clean water. Treat the water with stabilizers and wait for the environment to become stable before re-introducing your fish. In the meantime, ask your local acquarium shop to help you diagnose your pet's illness by the symptoms it exhibits, treat him with the medication they recommend and maintain the stability of hiss environment in order for your goldfish to have the best chance at recovery.

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Goldfish Diseases and Their Symptoms