Popeye Disease In Fish: Causes, Treatment & Prevention

Popeye is one fish disease you really want to avoid. This is not only quite painful (and potentially dangerous) for your fish, but it is also a problem to manage!

But as an aquarist, it’s important to understand this disease and what you can do to protect your fish.

This resource will teach you about the symptoms, causes, and treatment options for Popeye’s disease. Being prepared is absolutely essential if you want to protect your tank.

What is Popeye disease?

Popeye’s disease is a condition that causes a fish’s eye to bulge, bulge, or protrude from the socket. Scientifically, the disease is known as exophthalmos.

The bulging appearance of the eye is the result of fluid buildup. Fluid can accumulate behind the eye or in the eye itself (it all depends on the cause of the disease).

Popeye’s severity can vary quite a bit. In milder cases, the eye may remain clear with only moderate swelling.

However, more severe cases of the disease can damage the cornea, creating a cloudy appearance. If left untreated, the swelling can become so severe that the eye will rupture and fall off.

To make matters worse, popeye is usually accompanied by other health issues. Opportunistic bacteria can take hold, leading to serious infections. The same goes for fungal problems.

Popeye can affect all fish, regardless of species or environment. It also affects freshwater and saltwater fish.

Author’s note: Sometimes fish will only have Popeye disease in one eye. These cases are one-sided. When both eyes are bulging, the condition is a case of bilateral popeye.


Symptoms of Popeye’s disease in fish are subtle at first, so it can be difficult to catch the disease before it does damage. As a rule, the eye protrudes only slightly at first. But within a few days, the swelling can swell significantly and even affect the skin surrounding the eye.

In terms of behavioral changes, you may notice less activity. The fish can spend more time staying hidden. They might even show a disinterest in food.

Is it serious?

Popeye’s disease is a serious illness that requires immediate care. The earlier you are able to provide treatment, the better the prognosis.

In most cases, the disease itself is not fatal. However, there are so many additional issues that could affect your fish. For example, your fish could go blind in one or both eyes.

Infected eyes can break down and fall off without treatment. In unilateral popeye disease, fish can still recover after losing a single eye. But, their quality of life will be seriously affected. Potential care issues are only exacerbated if they lose both eyes.

You will need to make changes to help keep your fish healthy. Carnivorous or predatory fish will need time to adapt to the drastic change. During this time, peaceful fish will be more vulnerable to attacks from others in the tank.

Beyond the eyesight issue, you also have to worry about the effects of other infections. Popeye can quickly cause sepsis. This happens when the infection travels through the bloodstream.

It’s a deadly infection. In most fatal cases of popeye, sepsis is to blame. It can cause organ failure throughout the body. Your fish can also succumb to parasitic infections and a host of other potentially dangerous issues.

Needless to say, Popeye’s disease is a serious problem that you should not ignore!

Common causes

There are a few potential causes you will need to consider. If your fish suffers from unilateral popeye disease, a likely culprit is physical injury.

Fish are injury-prone creatures. Temperamental and very active species are more at risk. The fish might accidentally hit a rock and scratch their eye. Since they have no eyelids, fish are unable to provide last second protection to their eye in these cases.

Your fish could also have gotten into a skirmish with another fish in the tank. Alternatively, you might have accidentally injured your fish with a net.

Either way, the injury likely triggered an immune system response. This response is what causes the swelling.

Take a closer look at the eye to be sure. Often you can see a scratch or a physical sign of injury.

Another common cause is an internal infection. Fish that suffer from other ailments often suffer from popeye. For example, kidney failure, dropsy, or serious metabolic problems can cause fluid buildup.

One of the most common causes of popeye is poor water quality. This is often the case with bilateral popeye.

Author’s note: Interestingly enough, it’s not sudden drastic changes in water conditions that will put your fish at risk. Long-term continuous exposure to poor water quality is what you need to worry about.

Popeye’s disease regularly causes problems in overcrowded tanks or those that are not maintained as they should be. Regular exposure to high levels of ammonia and nitrate is thought to be to blame. Superstitious gases in unsanitary conditions are also likely to endanger fish.

Although you may only see one fish with popeye, others are at risk when conditions aren’t right. You will need to take quick action to ensure that other fish do not succumb to the disease as well.

Treatment of Popeye’s disease

Treating Popeye’s disease is not easy. Not only do you need to treat the underlying cause, but you also need to treat potential bacterial infections.

Here are the steps we recommend for the treatment of Popeye’s disease:

1. Check the water and make the changes

Start by checking the water conditions. If the ammonia and nitrate levels are detectable, you should make changes to fix the problem as soon as possible. Also check the pH levels and temperature to make sure the settings are within the acceptable range for your fish.

To protect other fish in the tank, perform water changes to improve conditions. You may also consider doing a thorough deep cleaning to remove waste and control ammonia levels.

2. Quarantine infected fish

In the meantime, it is best to remove infected fish. Place them in a separate quarantine tank with optimal water conditions.

3. Add salt

To reduce swelling, you can treat the fish with Epsom salt. Add between one and three teaspoons of Epsom salt for every five gallons of water in the treatment tank.

This should help reduce swelling over the next few days. As long as the water conditions are stable, the corneal lesions should also heal. During treatment, feed your fish a balanced diet rich in vitamins.

4. Treat bacteria

Next, you will need to tackle the bacterial issues. This is where things get complicated. You can use standard antibiotic and antibacterial products to prevent worsening bacterial infections and corneal damage.

These are the types of products that are used to treat conditions such as fin rot and infections. Generally, these products are applied directly in water.

To treat internal infections, you will need a broad-spectrum antibiotic. These are usually recommended by a veterinarian and are administered orally. They come as food, making it easy to target bacterial issues from within.

Treatment can take several months in severe cases of popeye. Continue to monitor your fish and water conditions. Over time, the eyes should deflate and return to normal.

To be on the safe side, you can also treat the main reservoir with antibiotics. If a fish has been affected due to poor water conditions, other fish in your aquarium are still at risk.

Improve water conditions and use an all-purpose antibiotic to be on the safe side!

Prevention options

The best thing you can do is take action to prevent popeye from happening in the first place! Because this disease is caused by so many things, there is no single method to prevent it. You will need to be proactive and consider all potential causes.

Start by taking a look at your tank setup. If it’s overcrowded, consider upgrading to a larger tank or moving some of the fish. Give your fish enough space to swim and breathe!

Bigger tanks are always better. With larger tanks, waste problems are less likely because the volume of water easily dilutes toxic chemicals.

To avoid poor water conditions, check levels regularly. Perform 20% water changes every week and make sure your filter is in good condition.

Ideally, ammonia and nitrate levels should be undetectable at all times. If the compounds are detectable at any time, your tank may still be overcrowded. Alternatively, your filter may not work as it should.

When you feed your fish, give them just enough food to eat in two minutes. If there are any leftovers, remove them from the tank. This will preserve water quality and reduce the chances of your fish suffering from popeye.

Finally, you can modify the decor of your tank to avoid accidental injuries. Get rid of sharp edges or abrasive stones. A few stones and driftwood are needed. But they should be relatively rounded and safe for all fish in the tank.

Author’s note: You may also want to rethink how you interact with your fish! Ditch the itchy threads and be a little gentler when cleaning or moving decorative items.

Preventing Popeye’s disease is quite easy. Just adopt good care habits and keep an eye on your fish. If you notice any problems with dangerous objects or water parameters, take the necessary steps to keep your fish safe, healthy and happy.

Final Thoughts

Popeye’s disease in fish is not funny. It is dangerous, painful and difficult to fight.

But that doesn’t mean you can’t do anything.

As you can see, there are many options for diagnosing, treating, and preventing Popeye’s disease in your aquarium. Be consistent with your efforts to protect your fish, and they will thrive as a result!

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