How to Manage Pop-Eye in Aquarium Fish

Telescope Eye Goldfish
Matteo Tarenghi

Pop-eye, also known as exophthalmia, is not a disease itself, but rather a condition in which the eye of the fish is swollen and protrudes abnormally from the eye socket. A single eye may be affected, or both eyes. In some cases, the eye may be cloudy, other times it will look normal other than being swollen. This condition is an indication of an underlying disease or disorder and should be investigated promptly.

When are Protruding Eyes Normal for Fish?

Keep in mind that some fish have been bred to have protruding eyes normally. For instance, Black Moor Goldfish are known for their large telescope eyes, which are perfectly normal and healthy. Celestial Eye Goldfish have eyes that protrude and point upward. These, too, are perfectly healthy.

Symptoms of Pop-Eye in Fish

Pop-eye is not a disease itself but is a symptom of an underlying disorder or condition. Fish that normally do not have telescoping eyes will display a marked swelling of one or both eyes. The eye itself may remain clear, or be cloudy or discolored. If the eye has suffered a physical injury it may also be bloodstained. In cases of severe pop-eye, it is possible for the eye to rupture. In such cases, the fish may eventually recover but will be blind in the affected eye.

  • One or both eyes protrude
  • Eye may be cloudy
  • Eye may be bloodstained
  • Eye my rupture

Causes of Pop-Eye in Fish

Multiple causative agents can be responsible for pop-eye. Sometimes the true underlying disorder is never determined, but it is always advisable to attempt a diagnosis.

Water chemistry: If only one eye is affected, it is less likely to be caused by problems with the water chemistry. This is particularly true if only one fish is exhibiting pop-eye.

Physical injury can cause a swollen eye, and quite often only a single eye will be affected. The injury could be due to a fight with another fish or scraping the eye against an abrasive object in the tank. Sometimes it is possible to see the damage to the eye, which is a dead giveaway that exophthalmia is the result of an injury. In most of these cases, the pop-eye will eventually resolve as the eye heals. However, the fish should be monitored closely, as infection can set in and must be treated promptly. Should the injury be severe, the fish may lose sight in the affected eye.

Infection: Another cause of pop-eye is an infection. Although infection can affect a single eye, it is more likely to affect both eyes than an injury will. The infection may be caused by a variety of organisms, including bacteria as well as parasites. If the fish suffers from both pop-eye and dropsy, the prognosis is more bleak, although fish can recover from dropsy with prompt and proper treatment. Internal problems, such as kidney failure resulting in the fluid build-up, can also case pop-eye.

If a metabolic issue, such as organ failure, is the cause, the prognosis is extremely poor.​ ​

Poor water condition can also cause pop-eye. Fish that are more sensitive to water conditions will be affected first, but if the water parameters are very poor pop-eye will eventually affect most or all of the fish. Any time there are multiple fish displaying pop-eye, the water should be tested to determine if something is amiss with the water chemistry. In cases of sub-par water chemistry, the eye may be cloudy as well as swollen. Cloudy eyes are quite often a sign of a problem with water parameters.


Treatment for pop-eye will depend upon the underlying cause. If the eye has been injured, palliative care using aquarium salt unless contraindicated, while the eye heals is advisable. Regular water changes are also recommended, as well as monitoring of water chemistry. If water tests indicate a problem, either with drifting pH or elevated ammonia or nitrites, it should be corrected promptly. Fish should be fed good quality foods to support a healthy immune system.

Fish that are clearly suffering from an infection should be moved to a quarantine tank to avoid infecting other fish. They can also be treated with broad-spectrum antibiotics to resolve the infection. If several fish are infected, it may be necessary to treat the main tank with broad-spectrum antibiotics. Keep the tank very clean, and perform regular water changes weekly.

  • Water changes
  • Use aquarium salt
  • Correct water chemistry
  • Good tank maintenance
  • Broad-spectrum antibiotics
  • Quarantine infectious fish
  • Feed high-quality foods

Prevention of Pop-Eye

Because pop-eye is caused by such a wide variety of issues, there is no single magic bullet that will guarantee it will never occur in your fish. However, if the tank is well maintained, partial water changes performed regularly, and the fish fed nutritional foods, the odds of pop-eye striking is greatly diminished. Monitoring the tank chemistry, and observing the fish daily for signs of illness will also help tip the scales in your favor. If the basics are followed, pop-eye will rarely occur, and when it does, it's not likely to prove fatal to your fish.

  • Regular tank maintenance
  • Regular water changes
  • Good nutrition
  • Monitor water chemistry
  • Watch for signs of illness