Pop-Eye Disease in Fish This article is verified by a vet

Sick goldfish lying in the bottom of the aquarium, The orange goldfish are sick and dying on the side of the air spray in the bottom of the aquarium.

With pop-eye disease, increased pressure causes the fish's eyes to bulge out.

If a fish’s one or both eyes bulge notably from its head, it seems listless, and is eating poorly, it is likely suffering from the rare pop-eye disease. Discover what this means for your fish in this article.

How dangerous is pop-eye disease for my fish?

The protruding “pop eyes” are usually not a disease in their own right, but rather a symptom of another fish disease. Increased pressure causes the fish’s eyes to bulge out, leading to pain for the creature.

To help your fish stock as soon as possible, it is therefore important to quickly identify the cause of the illness.

Symptoms: What signs do fish show with pop-eye disease?

Fish in both aquariums and ponds can suffer from pop-eye disease. The symptoms are usually easy to spot: 

  • One or both eyes significantly protruding from the head (exophthalmus) 
  • Cloudy eyes (similar to a thick, murky lens over the eye) 
  • Swelling of the conjunctiva 
  • Listlessness 
  • No or reduced appetite 
  • Pain 
  • Vision problems 

If one or more of your fish display signs of pop-eye disease, you should definitely contact your veterinarian.  

Diagnosis: How is pop-eye disease detected?

Diagnosis of pop-eye disease is made based on visible changes. However, a comprehensive discussion with the pet owner and a detailed, general examination are still essential.

In larger fish populations, pathological-anatomical, bacteriological, and parasitological examinations make sense. For this, your veterinarian often performs a swab. If multiple animals are affected, taking and examining water samples can also be helpful.

Treatment: How are the afflicted fish treated?

In general, you should treat sick animals in a quarantine tank and observe the remaining fish for signs of illness. Only reintroduce them to the aquarium or pond once they have fully recovered.

Medication

If bacteria trigger pop-eye disease, your veterinarian will provide an antibiotic to prevent further spread. The medication comes in the form of drops for the aquarium water or as medicated fish food.

Alder cones and/or Indian almond leaves may help as a supplement since they have anti-inflammatory and mild antibacterial effects. Additionally, they prevent fungal growth.

Supportive Measures 

Avoid stress at all costs. If poor water quality is the cause of pop-eye disease, perform a water change with treated tap water or salted reverse osmosis water to reduce germ pressure. 

In cases of gas supersaturation, refrain from changing the water until the pop eyes slowly regress. 

Prognosis: What are the chances of recovery?

Even with treatment, protruding eyes cannot always be cured. However, with timely treatment, pop eyes usually retract on their own.

If the cause is a high carbon dioxide content or gas supersaturation after a water change, blood vessels or tissues may also be destroyed in addition to pop-eye problems. In this case, the fish can die.

Fish that are severely affected and suffering should be humanely euthanized as painlessly and stress-free as possible.

Causes: What triggers pop-eye disease?

Pop-eye disease isn’t strictly a disease, but rather a symptom. There are therefore various causes for protruding eyes. It rarely occurs in completely healthy fish.

Various environmental influences can favour the outbreak of pop-eye disease. Poor water quality or even poisoning are some of the main causes.

Infections

Inflammation of the eye socket, kidney inflammation, and tuberculosis can lead to pop eyes. 

Marine fish tuberculosis (caused by Mycobacterium marinum) can also feature pop-eye as a symptom in the later stages of the illness. Tuberculosis always causes a severe disruption of general well-being, which you can notice from your fish’s behaviour.  

Dropsy

is caused by fluid accumulation in the body due to restricted kidney function, for instance from a bacterial infection like tuberculosis.

Kidney disease 

due to renal insufficiency causes water to accumulate in the fish’s body and eye sockets, leading to increased pressure that affects the eyes.

Eye injuries

An injured eye might significantly bulge; however, in this case, it is usually reddish and/or bleeding.

Gas supersaturation

often occurs immediately after a water change due to gas supersaturation in the tank, forming tiny bubbles in the aquarium and the fish’s tissues, which destroy tissue parts or clog blood vessels, thus causing pop eyes.

Poor water quality

is often the cause of pop-eye disease. Please check pH, KH, ammonium, nitrite, and nitrate levels. Excessive CO₂ levels can also be a cause of pop-eye disease.

Fat deposits

in the head area may push your fish’s eyes outwards.

Vitamin deficiency.

inadequate vitamin intake can lead to pop eyes.

Aquarium care is important © Andrey Nikitin / stock.adobe.com
Regular and thorough aquarium maintenance helps to prevent diseases.

Prevention: How can I protect my fish from pop-eye disease?

Make sure to regularly change the water in your aquarium and remove dead animals, decayed plants, and leftover food. Also, clean the filters and monitor the pH value and water temperature.

Moreover, you can support the immune system by feeding your fish a species-appropriate diet with high-quality fish food.

This article from zooplus Magazine is purely informative. If your pet is experiencing discomfort, contact your veterinarian for diagnosis and treatment.


Dr Julia Striegl, Veterinarian
autorenbild julia striegl mit hund

I studied veterinary medicine at LMU Munich, where I also finished my PhD in 2012. After that, I was able to gain a lot of experience, for example as a practicing veterinarian and scientific advisor. Particularly important to me is the continuous improvement of animal welfare and farm animal medicine. My greatest concern has always been to act in the best interest of my patients and to provide them with optimal care. In addition to my veterinary knowledge, I am happy to share my experience as a horsewoman and long-time dog owner, as well as a dog sportswoman.


Our most helpful articles
5 min

Butterfly Koi

Are you looking for new carps (Cyprinus carpio) for your pond? Then you should definitely consider the Butterfly Koi. Read in this article the most important information on this beautiful Koi.

7 min

Blue-Green Algae – Identification and Prevention

Blue algae looks like a green-blue carpet which can cover plants, decorations, and the bottom layer of the aquarium. Not only are they an eyesore, but blue-green algae can pose a significant risk to all forms of life in the aquarium. But what actually are they, and how do they grow? Read on to find out how to effectively combat and prevent the build-up.

6 min

Do Fish Feel Pain? Here’s What Science Says

Aquarium enthusiasts and animal-loving anglers might at some point ponder: do fish feel pain? Since fish can't speak, finding a satisfactory answer is not straightforward. However, a foray into science does offer better insight into the pain perception of fish.