Eye Diseases in Goldfish

Updated November 21, 2016

Goldfish diseases can be a difficult problem to diagnose and treat without expert knowledge. Eye diseases are often caused by bacterial or fungal infections or parasites, and if they are not treated, the infection may cause permanent blindness, eye loss or death. Maintaining a healthy aquarium environment and not overfeeding are a crucial defence against disease.

Cloudy Eye

Cloudy eye is characterised by an opaque, milky or cloudy film covering the surface of the eye, and in some cases there is also a build-up of mucus. There are numerous causes including a lack of vitamins in the diet, poor water conditions or parasitic flukes such as diplostomum. To prevent the disease from worsening, the water quality must be improved. This could involve using a filtration system, replacing a quarter of the water in the aquarium with freshwater and removing decomposing organic matter. An aquarium siphon, which can be found in most pet stores, can be used to vacuum up debris on the bottom of the aquarium. Changing food to a high-quality, vitamin-rich goldfish food may also help cure cloudy eye.


Pop-eye is characterised by one or both eyes protruding in a way that is not normal for that particular breed of goldfish. In the case of black moors, celestials or bubble eye, the eyes naturally protrude but if pop-eye is present, the eyes will appear much more swollen and prominent than normal. Causes for pop-eye may be abdominal dropsy, which will eventually also be characterised by raised scales on the body, or it could be caused a disease known as "hole in the side" disease, tuberculosis or fluid build up due to bacterial infections. Sick fish will need to be isolated by placing them in a separate tank and treated with an appropriate antibacterial remedy or medicated foods found at aquarium supply stores.

Saprolegnia Fungus

Saprolegnia fungus is a filamentous fungi that is a common problem in a pond or aquarium. It is an opportunistic water mould and feeds by secreting digestive enzymes onto the surrounding area. The result of this is a break down of cells and body tissue that help the fungus absorb nutrients. Saprolegnia often affects the body of a fish already weakened by disease or injury. It can attach itself to the eyes and the body, and it appears as whitish tufts or filaments on the eye surface. Large amounts of decomposing organic matter in the aquarium can contribute to fungal diseases, so it's necessary to keep the aquarium or pond clean, removing waste and not overfeeding. An appropriate fungicide for goldfish may prevent death.

Treating Fish Diseases

Knowing how to accurately diagnose and treat fish diseases in the early stages is crucial in preventing serious problems or death. Finding an expert is necessary if you are not confident in handling the matter yourself. Help and advice can often be found in aquarium stores or freshwater fish suppliers. If they don't have the answers, they may know of an expert who does.

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