Why Is My Fish’s Eye Cloudy?

CLOUDY EYES Longhorn Cowfish

Longhorn cowfish with cloudy eyes can be a cause for concern, but it’s often treatable. Cloudy eyes, or corneal opacity, is a symptom of underlying issues rather than a specific disease itself

Here are the most common causes and how to address them:

Causes

• Poor Water Quality: This is the most frequent cause. Longhorn Cowfish, like other marine fish, are sensitive to ammonia, nitrite, nitrate, pH imbalances, dissolved organic compounds, and heavy metals. Poor water quality can irritate and inflame the cornea, leading to cloudy eyes.
• Bacterial Infections: These can develop from minor injuries or when a fish is stressed or has a weakened immune system. Bacteria like Aeromonas, Vibrio, and Pseudomonas can cause eye infections leading to cloudiness and inflammation.
• Physical Trauma: Longhorn Cowfish can injure their eyes by scraping against decorations, fighting with tank mates, or during handling or tank maintenance.
• Nutritional Deficiencies: A lack of a healthy, balanced diet, particularly vitamin A, can contribute to poor eye health and cloudy eyes.
• Parasitic Infections: External parasites like marine ich or flukes can irritate the eye tissue and cause cloudiness.
• Age-Related Issues: Older Longhorn Cowfish may develop cataracts or other age-related eye changes that can cause cloudiness.

Actions to take

1. Test Water Parameters: Begin by checking your aquarium’s ammonia, nitrite, nitrate, pH, temperature, and salinity levels. If any are outside the ideal range for Longhorn Cowfish (see next section), take steps to correct them.
2. Perform Water Changes: Regular water changes (25-30% weekly to bi-weekly) are essential to maintain good water quality and prevent the build-up of harmful substances.
3. Enhance Filtration: Ensure your filtration system is functioning optimally and consider adding a protein skimmer to further improve water quality.
4. Evaluate and Improve Diet: Longhorn Cowfish are omnivores and should be fed a varied diet including meaty foods (shrimp, bloodworms, chopped clams) and herbivore preparations like spirulina or algae wafers. Ensure they receive plenty of vitamin A.
5. Inspect the Aquarium for Hazards: Remove any sharp decorations or rockwork that could injure your Longhorn Cowfish’s eyes.
6. Consider Antibiotics (If Infection Suspected): If you suspect a bacterial infection, broad-spectrum antibiotics may be necessary. It’s best to consult with a veterinarian or experienced aquarist to choose the appropriate medication and dosage. API Melafix is an all-natural antibacterial treatment that works to treat infections in fish. This product may be used when adding fish to an aquarium to smooth the transition from store to home or if an infection is suspected.
7. Consider Anti-parasitic Treatment (If Parasites Suspected): If parasites are the suspected cause, anti-parasitic treatments like copper or freshwater dips may be necessary. Again, consulting with an expert is recommended.
8. Quarantine the Affected Fish: If the cloudy eyes are due to a suspected infection, it’s best to move the affected Longhorn Cowfish to a separate quarantine tank to prevent the possible spread of disease and to facilitate individual treatment.
9. Reduce Stress: A low-stress environment with plenty of hiding places, a consistent light cycle, and avoiding sudden changes in the tank environment can aid recovery.

Longhorn Cowfish tank requirements

• Minimum Tank Size: 180-250 gallons for a single Longhorn Cowfish
• Water Conditions: pH: 8.1 – 8.4; Salinity: 1.020 – 1.025; Water Temperature: 72°F – 78°F.
• Water Flow: Moderate to high flow is preferred.
• Substrate: Sandy substrate.
• Décor: Plenty of live rock and hiding spaces.
• Diet: Omnivore. Provide a mix of meaty foods (shrimp, bloodworms, clams, mussels, snails, tunicates, fish) and algae-based foods. 

As dedicated reef aquarium keepers, whenever we notice something unusual with one of our fish, it can feel alarming. One common issue is noticing a hazy or cloudy appearance in a fish’s eye, and we immediately start to worry. Is it serious? Can it be treated? Is my fish in pain? Will my fish be ok?

In this article, we will examine why your fish’s eye may have turned cloudy, the treatment you can try, and how to prevent a cloudy eye from happening in fish.

What Is “Cloudy Eye”?

A cloudy eye (or corneal/eye opacity) is not a fish disease, but rather a common symptom of different underlying conditions. When a fish’s eye becomes cloudy, the outer protective layer of the eye (the transparent cornea) becomes infected, damaged, or inflamed. 

Your fish’s eye may appear anything from slightly foggy to completely white, and it can affect one eye or both your fish’s eye.

Why Did My Fish’s Eye Turn White?

There are seven common causes of cloudy eyes in reef fish. 

1. Poor Water Quality 

The most common cause of cloudy eyes is usually poor water conditions. As your fish’s eye is directly exposed to water in aquatic environments, fish can become sensitive to improper pH levels, dissolved organic compounds, accumulated heavy metals, high ammonia nitrate concentrations, and elevated ammonia/nitrite levels. 

All the above cause irritations and can cause cloudy eyes due to the inflamed cornea.

• Problem: This is the most frequent cause of cloudy eyes in aquarium fish. Unsuitable pH levels, high concentrations of ammonia, nitrates, or nitrites, or accumulated heavy metals in the water can irritate the fish’s eyes, leading to inflammation and cloudiness.
• Solution:
  • Test your water parameters regularly, including ammonia, nitrite, nitrate, and pH levels.
  • Perform regular water changes (e.g., 25-30% weekly) and ensure proper filtration to maintain a stable and healthy environment.
  • Clean or replace filter media as needed and ensure your protein skimmer is working efficiently.
  • Use a quality water conditioner to neutralize chlorine and chloramine in tap water.
    

Poor water quality is a prevalent cause of cloudy eyes in fish. High levels of toxins like ammonia, nitrites, and nitrates can irritate a fish’s eyes, leading to cloudiness. Such conditions stem from overfeeding, overcrowding, or inadequate filtration.

Poor water quality also lowers your fish’s immune system, making it susceptible to bacterial and fungal infections.

Diagnosing the Cause

You need to conduct a water quality check to see if poor water quality causes cloudy eyes in your fish. Testing the water for ammonia, nitrite, and nitrate levels will help determine if the cloudiness is due to a toxic environment.

Also, watch your fish’s behavior — if they seem less active or are gasping at the surface, your water might be the problem.

Treatment Options

Improving water quality involves regular water changes, proper tank maintenance, and ensuring the filtration system functions correctly.

It may also require reducing the number of fish or the amount of food given if overstocking or overfeeding is an issue.

Completely replacing the aquarium water isn’t advised because it will remove the beneficial microorganisms and disrupt the nitrogen cycle in the tank, which could be harmful to your fish.

2. Bacterial Infections

Secondary bacterial infections usually develop from minor eye injuries when fish become stressed or their immune system weakens. Common bacterial pathogens that cause severe eye infections in fish include Aeromonas, Vibrio, and Pseudomonas species. They quickly develop into cloudy eyes, inflammation, and in severe cases discharge.

• Problem: Bacteria, such as Aeromonas, Vibrio, and Pseudomonas, can infect the cornea, causing cloudy eyes, swelling, and even discharge.
• Solution:
  • If the cloudiness is accompanied by swelling or discharge, it may indicate a bacterial infection.
  • Consult with an experienced fish veterinarian or specialist for accurate diagnosis and appropriate antibiotic treatment.
  • Consider using reef-safe antibiotics or medicated food in a quarantine tank. 

3. Fungal Infections

Fungal infections, such as those caused by Saprolegnia or Ichthyophonus hoferi, often emerge when fish are most vulnerable — due to injury, stress, or suboptimal living conditions like poor water quality or overcrowded tanks.

Visible signs include cotton-like growths on the fish’s body, including the eyes, and if left untreated, can lead to more severe complications like septicemia or fin rot.

Fungal infections often occur in tanks with substandard water quality, poor oxygenation, or high ammonia levels.

Stress factors such as low water temperature, lack of aeration, or overcrowded tanks also contribute to the vulnerability of fish to fungal infections.

Diagnosing the Cause

To determine if a fungal infection is behind a fish’s cloudy eye, look for accompanying signs like white or grey fuzzy patches on the eye or body. These growths can resemble cotton and are not typically seen with bacterial infections.

A definitive diagnosis often requires a vet’s examination of the affected tissue. Water quality tests are also crucial, as poor conditions commonly contribute to fungal outbreaks.

If these signs are present and water quality is poor, a fungal cause is likely.

Treatment Options

Treatment of fungal infections generally includes medicating the water with substances like potassium permanganate, especially for Saprolegnia. For Ichthyophonus hoferi, raising salt levels and water temperature may be effective.

Maintaining good water quality, proper aeration, and appropriate tank temperature are essential preventive measures.

4. Parasitic Infections

Parasites such as marine ich, marine velvet, flukes, and other external parasites can cause irritation which leads to cloudy eyes in fish. These parasites directly attach to the eye tissue and need treatment asap to prevent the fish’s vision from worsening.

• Parasitic infections: External parasites like flukes can attach to the eye, causing irritation and cloudiness. Treatment may involve anti-parasitic medications.

Parasitic infections in fish can lead to various symptoms, including cloudy or milky eyes.

These infections are typically caused by parasites that invade the eye or the surrounding tissues, such as flukes or protozoa, which can be introduced into an aquarium through new fish, plants, or even replacement water.

Diagnosing the Cause

A fish with a parasitic eye infection may show other signs of distress, including abnormal swimming, inflammation, and visible parasites on the eye, which can be dangerous for the fish if not promptly addressed.

You should also consider the fish’s history, whether you have recent additions to the tank that might have introduced parasites.

Veterinary consultation is necessary since specialized equipment is needed to identify the parasites that have infected your fish.

Treatment Options

Treating parasitic infections that cause cloudy eyes generally involves anti-parasitic compounds like praziquantel for flukes and metronidazole for protozoan infections.

The treatment plan may include administering medication directly into the water or via food if the fish are still eating.

Complete eradication of parasites requires following a strict medication schedule, which may involve increasing the water temperature to speed up the life cycle of the parasites, making them more susceptible to treatment.

Improving tank conditions and conducting regular water changes are vital to aid recovery and prevent future infections.

5. Physical Trauma

Fish can sometimes injure their eyes by scraping against decorations or rough rockwork inside the aquarium. This is why it is important to create an aquascape that is safe for marine fish. 

Fish can also injure their eyes if they have aggressive encounters with tankmates, accidental injuries during netting (when catching your fish), aquarium tank maintenance, or hitting aquarium glass if they become startled.

• Problem: Fish can injure their eyes by scraping against tank decorations, during netting, or in aggressive interactions with other fish. Fish lack eyelids, making them particularly vulnerable to eye injuries.
• Solution:
  • Ensure your aquascape has smooth edges and plenty of open swimming space to minimize the risk of collisions.
  • Handle fish with care, using soft nets and ideally coaxing them into containers for transfers.
  • Maintain a low-stress environment with hiding places for the fish to recover from any injury.
  • Clean water is crucial for healing. 

Physical injuries are also common causes of cloudy eyes in fish. Such injuries can occur when fish collide with sharp tank decorations or are handled roughly.

The absence of eyelids in fish means their eyes are more exposed and susceptible to injury.

Without the protection eyelids provide, fish can easily suffer from physical abrasions caused by tank decorations, substrate, or aggressive behavior from other fish.

This vulnerability can contribute to the development of cloudy eyes, as the exposed tissues are more prone to damage and subsequent infection or inflammation.

Diagnosing the Cause

In diagnosing whether the cloudy eyes of your fish are caused by trauma or physical injury, check for signs of damage to the fish’s body or fins.

If a collision or fight causes trauma, injuries in other parts of the body could also be present. Usually, only one eye is also affected. The area around the cloudy eye may also have visible signs of wounds or abrasion.

Treatment Options

The primary treatment for physical injuries is to provide a clean and safe environment to prevent infection. This includes removing sharp objects from the tank and ensuring optimal water quality.

Sometimes, a mild antiseptic may be used to prevent secondary bacterial infections.

6. Age-Related Changes

Just like us humans, fish can develop age-related eye changes such as cataracts that can turn into cloudy eyes. This is most common in older fish and those with longer lifespans.

• Aging: Older fish can develop cataracts, which are a natural clouding of the lens, affecting vision and causing eyes to appear opaque. Unfortunately, cataracts are often irreversible. 

7. Nutritional Deficiencies

• Nutritional deficiencies: A lack of essential vitamins, particularly vitamin A, can negatively impact fish eye health and lead to cloudiness. Ensure your yellowtail cowfish receives a balanced and varied diet, including foods rich in vitamins and Omega-3 fatty acids, according to Vision Source El Dorado and Whidbey Island Seafood Company.

Providing fish with a healthy balanced diet and good nutrition is essential for their health. In particular, vitamin A is important for fish, as deficiencies can lead to eye problems.

Cloudy eyes can also be a symptom of a poor diet, leading to a weakened immune system.

Diagnosing the Cause

Cloudy eyes caused by poor diet and nutritional deficiency are usually accompanied by other signs and symptoms, such as lethargy, fading colors, and stunted growth.

Treatment Options

Addressing cloudy eyes caused by nutritional deficiency requires a varied diet that meets all their dietary needs.

This could include high-quality flakes, pellets, frozen or live foods, and vegetable supplements. Targeted supplements may be recommended for specific deficiencies to address the lack of certain nutrients.

8. Species-Specific Considerations

Some species of fish are more prone to eye-related issues. For example, some surgeonfish are more likely to form eye cloudiness. 

Puffers and boxfish are also known to develop eye issues because they have protruding eyes. Bottom-dwelling fish also, as they spend more time around the sand substrate, which can irritate their eyes. When cleaning the sand substrate inside your aquarium, be careful not to blow sand in their face which could lead to irritation.

Is Cloudy Eye In Fish Contagious?

Cloudy eyes can be contagious, depending on the underlying cause. Cloudy eyes from bacterial or parasitic infections can be contagious. Fish that are stressed or have a weakened immune system are more likely to contract cloudy eyes. Therefore, you should separate and quarantine your fish to prevent it spreading to other livestock inside your aquarium.

Does My Fish Have Cloudy Eyes?

To determine if your fish has cloudy eyes, the first step is to diagnose the cause. You should ask yourself: 

Is the cloudiness in one or both eyes?

One-eye (unilateral) cloudiness typically suggests a localized infection or trauma. Bilateral (both eyes) cloudiness usually is a sign of an infection, nutritional issues, or water quality problems. 

Does your fish have any other symptoms?

Other symptoms that may accompany a cloudy eye include loss of appetite, skin lesions/discoloration, abnormal swimming patterns, behavioral changes, and/or rapid gill movements. 

How quickly did your fish develop a cloudy eye?

Sudden eye cloudiness usually indicates an acute infection or an injury, while gradual cloudiness may be from chronic, degenerative, or nutritional issues. 

What do your water parameters read?

Check the water parameters inside your reef aquarium. Specifically, test the nitrate, nitrite, pH, ammonia, temperature, and salinity levels to rule out any problems with the water quality. source

How To Fix Cloudy Eyes In Fish?

The first step is to address the water quality. 

If you suspect poor water quality:

• Perform a 25-30% water change and clean the mechanical filtration media

• Replace and add fresh activated carbon (carbon media)

• Check that your protein skimmer is running properly

• Test and adjust water parameters if needed

Next, treat any infections.

If your fish has a bacterial infection, use antibiotics that are reef-safe. For extreme infections, you may want to consider removing your fish and treating it with antibacterial foods or a medicated bath. When medicating fish it is important to always quarantine fish.

For parasitic infections, use copper treatments (never dose copper in a display tank), freshwater dips that are properly pH-matched, or formalin dips (only to be used for short-term treatment). 

If your fish has experienced physical trauma to its eye, clean water is the best medicine. If the injury doesn’t seem to get better, consider using iodine supplements (always check the dosing guidelines). To help with the healing process, ensure you maintain optimal conditions and maintain a low-stress environment with plenty of hiding spaces for your fish to rest. 

If nutritional deficiencies are the cause of cloudy eyes,

• Marine algae such as Tetraselmis chui, Rhodomonas salina, or Tisochrysis lutea

• Frozen foods like brine shrimp or mysis shrimp

• High-quality marine flakes/pellets

• Foods rich in vitamins

Preventing Cloudy Eyes In Fish

To prevent cloudy eyes, you should:

• Maintain stable water parameters and water chemistry

• Monitor filtration and change filter media when needed

• Design a safe aquascape for fish with smooth edges and plenty of swimming space

•  Quarantine ALL new additions to prevent unwantedaquarium hitchhikersand fish diseases

• Stock compatible fish to prevent aggression

• Feed a high-quality and varied diet

• Handle fish with extra care when transferring fish to a new aquarium 

• Follow proper acclimation methods

When To Seek Expert Help For Cloudy Eyes In Fish?

Most cases of cloudy eyes can be treated at home, however, sometimes professional assistance is needed if:

• The eye is severely swollen

• The eye is protruding

• The fish is showing signs of stress or pain

• The condition is worsening despite home treatment

• Your fish is also showing severe discoloration or unusual growths on the eye or body

If you notice any of the above, speak to a fish veterinarian or experienced specialist.

Conclusion

A cloudy eye in fish should never be ignored, but also try not to panic. By understanding the common causes of cloudy eyes in fish and the home treatments available, you’re on the right track to helping your fish.  source