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Why Is My Molly Fish Eye Bulging (Popeye)?

For any aquarist, nothing is scarier than watching aquarium fish in pain or injured. If you have molly fish in your tank, there are some common diseases or injuries you should know about. One of them is Fish Eye Bulging.

If your fish’s eye is swollen or protruding abnormally from its socket and you want to know “Why Is My Molly Fish Eye Bulging,” this article is for you.

In this article, we will understand the reasons behind your molly fish’s eye bulging and will know how you can prevent and cure it in time to avoid any severe problems in the near future.

Popeye” is the term used to describe the bulging of either one or both of the fish’s eyes. Want to learn all about it?

So without further ado, let’s get into it –

Why Is My Molly Fish Eye Bulging?

why is my molly fish eye bulging
Typically the primary reasons for your molly fish’s eye bulging are poor aquarium water conditions, physical injury to the fish’s eye, and infection. The continual exposure to chronically poor water conditions having high levels of Ammonia nitrites and Nitrate is generally the cause of fish eye swelling.

Overcrowded aquariums with infrequent water changes are yet another cause for popeye in mollies.

If your molly fish’s eye is bulging, it could also be a sign of other health issues, like kidney failure, Dropsy, etc. that can also cause fluid buildup resulting in popeye.

why is my molly fish eye bulging

                    A Black Molly Fish With Popeye

Bulging Eye Of Molly Fish: Explained

A Molly fish’s eye swelling results from fluid leaking behind the eyeball. When the amount of fluid increases, pressure builds up, pushing the fish’s eyeball outward.

In severe cases, if the affected eyes rupture completely or the cornea is ruptured due to swelling, the eye might appear cloudy, red, or discolored, and in the worst case, the fish may lose the ability to see, or the eyes fall off the fish.

Depending on your fish’s situation, the fish may find it difficult to eat or find food in the aquarium, so you should offer the fish a vitamin-rich diet and assist the fish in eating it so it can recover.

Now Let’s learn about the causes of popeye in detail. These are the four common causes of eye bulging in fish:

1. Physical Injury

The eye bulging in mollies can happen due to injuries caused by encounters with other fishes in the same tank. The injury can also be due to rough handling, or it’s just the collisions with an object where the fish scraped its eye against it. All of these could cause your fish’s eye to pop out and also cause stress to your fish.

2. Overcrowded tank

Popeye in mollies can also happen due to overcrowding in the tank. The water quality deteriorates quickly in overcrowded tanks due to the accumulation of excessive waste in the tank. If the water is not changed on a regular basis, then there is a greater chance of popeye to your dearest molly.

3. Infections

Infections caused by the bacterial, parasite, fungal diseases, or other internal infections are also one of the major causes of popeye in mollies.

Bacterial infections can cause popeye in fish by attacking the tissue around the eye, which builds fluid behind the eye leading to swelling and inflammation. It can cause the eye to protrude from the socket. In severe cases, a bacterial infection can cause the fish’s eye to become cloudy or discolored and even lead to blindness.

4. Poor Water Conditions

If you don’t maintain proper water conditions in your aquarium, then it can cause “Popeye” in mollies. Poor water conditions in aquariums are often caused by poor filtration, low oxygen levels, and the presence of high levels of Ammonia and Nitrate.

Common Signs of Popeye in Fishes

Your fish may show some signs when they got Popeye disease.

These are the four common signs of Popeye disease in fish:

  • Cloudiness of the fish’s eyeball
  • Rupture of the eyeball
  • Discoloration or blood in the eyeball
  • Protrusion of one or both eyeballs

Types of Popeye Disease in Fish: Unilateral vs. Bilateral

Now, let’s talk about types of eye bulging (Popeye) in fish. The Popeye disease can be categorized into two types:

1. Unilateral Popeye
2. Bilateral Popeye

The main difference between unilateral and bilateral popeye is that Unilateral popeye refers to a condition in which only one eye is affected and is often caused by some injury rather than unfavorable water parameters. In contrast, bilateral popeye refers to a condition in which both eyes are affected, and the cause of it is generally poor aquarium water conditions.

The other difference is that Bilateral Popeye is relatively easy to cure compared to unilateral popeye. To treat Bilateral popeye, you can do a few things maintain the water quality in the aquarium, take proper care of your mollies, etc. While if it is unilateral popeye, then it will require special treatment from a veterinarian.

How to Treat Eye Bulging (Popeye) In Fish?

why is my molly fish eye bulging
You can do some things on your end to treat popeye in your molly fish; however, it’s always a good idea to consult with a veterinarian or fish specialist to determine the best course of action or medications.

Follow the tips below to treat popeye:

  • The first thing to do is to test your aquarium water’s quality and check if the water parameters are moderate. If the water parameters are not good, then you should increase the frequency of water changes in your tank.
  • You should also offer your fish a proper vitamin-rich diet as a diet along with improved water conditions can help your fish to recover minor corneal damage.
  • You can also use Epsom salt, which helps reduce the fish eye’s swelling. Adding one to three tablespoons per five gallons of water is recommended.
  • Keeping fish with a bacterial infection in a quarantine tank is also recommended to treat the fish with antibiotics suggested by a veterinarian.


So that’s it for today’s article. We hope you know why your molly fish eye is bulging.

In a nutshell, Eye infections caused by bacteria or parasites, Injuries to the eye, and poor environmental aquarium factors are the main culprits for fish popeye.

If you notice that your molly fish’s eye is bulging, it’s essential to observe its behavior and appearance and to take steps to address the potential underlying cause. It may involve cleaning the tank, testing the water quality, adjusting the water parameters, and providing your fish with proper nutrition and any necessary medication.