Popeye in Fish: 7 Main Causes and How to Treat

Experts intimate that cultured fish are prone to Popeye disease (exophthalmia) thanks to various stresses from different aquarium conditions. If your fish has the disease, you should look into it sooner than later. This article provides in-depth coverage of Popeye in fish, its leading causes, and treatment. 

Popeye in fish is mainly caused by stress due to poor tank conditions, infections, and aggressive behavior among tank mates. Immunological deficiencies and genetic factors also predispose fish to Popeye. Treating the disease involves antibiotics, aquarium salt, and performing palliative care. 

In this article, you’ll learn the seven leading causes of popeye in fish. Even better, you’ll discover the best treatment course to help your fish live a trouble-free life. Keep reading! 

7 Main Causes of Popeye in Fish 

It’s essential to know the primary cause of Popeye since various factors can trigger this condition. Let’s look in-depth into the seven main causes of Popeye disease in fish. 

1. Poor Water Quality

Popeye in Fish; causes and treatment

Poor water quality comes about when you don’t clean the tank regularly. 

If you don’t change the water regularly, the aquarium lacks a functional filter to eliminate impurities produced in the aquarium.

The condition inflicts plenty of stress on fish. If you don’t check the water chemistry regularly, you’ll notice some fish with protruding eyes—the first indication of Popeye.

If left unchecked, the following factors exacerbate the fish’s immunity:

  • High nitrates that lead to an overgrowth of green algae
  • The presence of ammonia is considered one of the most common problems in many aquariums. Ammonia is produced from fish wastes or rotting food leftovers in the tank. The gas is poisonous to fish, and any trace of it is dangerous to the ecosystem.
  • Nitrites also affect the fish’s expected oxygen consumption, just like ammonia. Methemoglobinemia is the condition where the oxygen supply in the fish’s bloodstream falls. Your fish won’t be able to breathe well.
  • Too high or too low a pH can disservice your aquarium fish. Most fish will not survive in highly acidic water as it burns their skin.
  • Too high or too low temperatures in the aquarium. Tropical fish would be okay with high temperatures but not low temperatures. Popeye would be rampant when temperatures fall. The same applies to extremely high temperatures that can trigger eyesores.
  • Unbalanced salinity is another surefire way of your fish getting Popeye. Adding a lot of saltwater to the aquarium is a serious trigger of high salinity that can disrupt the osmotic balance in the ecosystem.

Also Read: Molly Fish Eye Bulging: 3 Causes and Their Remedies

2. Physical Injury

A swollen fish eye could result from an injury due to different factors.  For instance, the fish entangled in a bun fight and one or both got injured. This is common in aquariums with aggressive species like Rosy Barbs, Tiger Barbs, and red-tail sharks.

Physical injury can also occur due to accidental collisions in the tank. The fish can hit itself unknowingly against the tank walls or objects in the tank, damaging eye tissues. Usually, such injuries are unilateral, meaning they affect only one eye.

Protruding eyes as a result of injuries subside on their own with time. However, it’s easy for a secondary infection to follow if you don’t observe necessary precautions like treating the fish.

3. The Trauma of Careless Handling

Careless handling during transportation and fish transfer from one place to another can cause trauma and shock. 

Let’s say you want to transfer your sexually active fish to a breeding tank. You’ll definitely damage the fish’s soft skin, including its eyes, if you use a fish net with sharp corners.

The fish can even give you a test of their stubbornness by jumping out of the net. This is a surefire way of sustaining serious injuries if they fall on the floor or against sharp objects.

Even worse, fish can be traumatized during transportation from one point to another. Even with the best shipment conditions, there are a few consequences due to secondary transportation effects.

This trauma worsens when fish are released into the new receiving water. If the water is low quality, your fish will be highly stressed – hence, unable to resist diseases such as Popeye.

For this reason, you should pay close attention to the tank and water before introducing the fish.

Find Out: Oscar Fish Hole in the Head: Cause and 4 Easy Treatments

4. Nutritional Deficiencies

Fish with Popeye disease

Many aquarists don’t suspect that nutritional deficiencies could cause Popeye. Often, they stop at other possible causes like poor quality water or infections, forgetting that the dietary requirements of various fish differ; thus, giving them the same food could be the greatest undoing.

Inadequate nutrition lays a good ground for weak immunity. Your frail fish would easily catch Popeye when they lack vital nutrients in the diet.

For instance, fish need vitamin C or ascorbic acid in plenty. Suppose it’s not provided, their health will slump. Your fish will have low immunity if they eat only one type of food.

Nutritional deficiencies may not affect your fish in a flush. They take time, and before long, effects begin to show up in the form of sickly fish. Once your fish starts becoming sick with other diseases, it’s only a matter of time before you see them with Popeye.

5. Infections

Bacterial infections are the most common suspects when diagnosing infections as the primary cause of Popeye. 

Bacteria are opportunistic; they take advantage of an injured fish and invade the ailing tissue.

The opportunistic nature of these pathogens is why you should help your fish recover from physical injuries sustained elsewhere. Once bacteria attacks the eye, they colonize its tissues, making it swollen.

Worst of all, bacterial infections can also lead to Dropsy in fish, a condition by which fluid builds up in the fish’s belly or body. Your fish will unlikely survive if the two conditions combine, even with the best interventions.

Check Out: 14 Common Angelfish Diseases and Illnesses With Their Treatments

6. Overcrowding

An overcrowded tank exposes fish to fights and bullying

Moreover, maintaining an overcrowded tank is difficult.

Therefore, your fish suffers a double tragedy—the physical injuries inflicted due to fighting and poor water conditions resulting from too much waste in the tank.

That said, the amount of stress a fish undergoes while in a tank full of other fish is overwhelming. It predisposes it to low immunity, lowering its ability to fight diseases.

7. Genetic Factors

Genetic factors may not be a direct cause of Popeye in fish, but they can play a significant role as far as the susceptibility of particular fish can go. 

When it comes to Popeye in fish, genetics play a role in the following ways:

  • Genetic Mutations: Some genetic mutations can cause defects in your fish’s eye structure. Therefore, any time it encounters a situation or eye infection (like Popeye), it will never be in the best position to resist the effects of the attack.
  • Weakened Immune System: Genetics determine how strong or weak a fish’s immunity turns out. Fish with weak immunity are highly susceptible to pathogens, including Popeye-causing bacteria.

Signs and Symptoms of Popeye in Fish

As the name suggests, Popeye disease’s main sign is that either one or both eyes of the fish appear popped from their sockets

Other than opped eye in fish, here are other notable signs and symptoms of Popeye in fish:

  • The eye area swells and becomes red due to tissue inflammation
  • The eyeball socket is stretched more than usual
  • The eye becomes cloudy or discolored
  • In severe cases, the eyeball raptures
  • The fish becomes weak; hence inactive
  • Fish loses appetite; it may start from eating less food to refusing it completely
  • Fish tends to hide all the time due to stressors
  • The body may swell, probably due to Dropsy
  • Fins clamp on the body

It’s worth noting that it’s hard to detect any signs during the early stages of the disease. Therefore, constant vet examinations are necessary.

Notably, Popeye disease symptoms vary from case to case because causal agents may be different. For example, Dropsy may accompany a bacterial infection rather than a plain physical injury.

Therefore, always consult your vet when you notice anything unusual on your fish. Early diagnosis and treatment will save your wet pet.

3 Ways to Diagnose Popeye in Fish

Popeye in fish illustration

Diagnosing Popeye in fish should be based on careful physical observation and examination. You should monitor your fish’s behavior and physical state to notice any unusual occurrences.

Remember to seek your veterinarian’s support for an accurate diagnosis. You can’t do it alone, especially if you don’t have enough experience handling such cases.

Here are the three best ways to diagnose Popeye in fish:

1. Visual Observation

Visual observation is probably one of the best methods for diagnosing Popeye for a layman.

You should observe the fish’s physical state, including its routine behavior, like swimming patterns, feeding, roaming, resting, and positioning in the tank.

Look for any signs of swelling around the eyes. This observation should be done very closely. Ensure to look from all angles—most fish can’t just stand there to be observed, so you must keep following them around.

A rule of thumb is to have white lights on for a clear view of the fish in the tank. Otherwise, you may not be able to catch the best part of the fish’s eyes.

2. Physical Examination

Observing fish with your eyes may not be enough to help you know if they’re suffering from Popeye, especially if the disease is in its early stages. Consequently, you should seek your vet’s services for a physical examination.

With such examination, a particular protocol to capture fish from the aquarium is vital. Remember, you don’t want to add to the pain your fish is already going through by manhandling it.

Even so, a gentle fish net collects the fish from the aquarium and places it in a shallow container with clean water. Then now, you can observe the fish closely from the container – remember to put it in a well-lit area. You can also use a magnifying glass to ensure you don’t miss out on details.

When observing the fish, look for redness around the eye, lesions, slightly swollen eyes, abnormal discharge, and other symptoms mentioned earlier.

3. Test the Water Quality

You can also test the aquarium water regularly to determine if it’s the cause. Testing the water helps you know whether its condition is okay for the health of the fish or suboptimal.

Make sure you use a high-quality testing kit to assess parameters such as;

  • Nitrites
  • pH
  • Nitrates
  • Ammonia
  • Hardness
  • Temperature

What Is the Best Way to Treat Popeye in Fish?

The best way to treat Popeye in fish is by using Epsom salt and antibiotics. Epsom reduces swelling effectively if you add the correct amount to the water.

The recommended amount of Epsom salt in an aquarium is ⅛ of a teaspoon for every five gallons (18.93 liters) of water. Therefore, you should put one teaspoon of Epsom salt in a 40-gallon (151.42-liter) tank.

The vet may recommend appropriate broad-spectrum antibiotics like erythromycin, Marden Maracyn or tetracycline if the Popeye is bacterial.

How to Prevent Popeye Disease in Fish

You can prevent Popeye disease in fish by providing the best palliative care. You should manage the aquarium conditions well. For instance;

  • Check the water quality regularly to ensure all parameters are at the correct, current levels
  • Minimize nitrates through partial water changes to prevent too much algea growth
  • Keep ammonia and nitrites at 0 ppm
  • Control temperature to keep it within the range your fish species would be comfortable. The optimal aquarium temperature for tropical fish is between 75 and 80℉ (23.89 and 26.67℃). Goldfish and other members of cold-water species thrive at 70℉ (21.11℃).
  • Keep the recommended salinity and acidity levels
  • Provide the correct water hardness depending on the species in question. Ideal freshwater aquariums should have a hardness of between 4-8 dGH. On the other hand, saltwater aquariums should have a hardness of around 7.5 dKH 
  • Feed your fish a balanced and nutritious diet for optimal immunity. You can supplement commercial fish pellets and flakes with live foods and vegetables like lettuce and squash 
  • Avoid keeping many fish species in the same tank to avoid aggression and overcrowding problems
  • Handle your fish properly when cleaning the aquarium or transferring them from one place to another. This reduces trauma and shock.

Final Thoughts

As a responsible fishkeeper, it’s your responsibility to understand the ins and outs of Popeye in fish for the well-being of your wet pet.

Now that you know the main causes of Popeye in fish, take the necessary measures to prevent them. 

In the worst case that your fish becomes infected with Popeye, follow the outlined steps for treatment. 

A rule of thumb is to incorporate constant vet examinations to diagnose the disease earlier for efficienct treatment.

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