Why Is My Fish’s Eye Cloudy?

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.

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. 

3. 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. 

4. 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. 

5. 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. 

6. Nutritional Deficiencies

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. 

7. 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. 

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, at Reefco Aquariums we recommend a varied diet including:

• 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 unwanted aquarium hitchhikers and 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. 

If you need assistance with your fish or advice from aquarium experts, contact the Reefco Aquariums team today - we are always happy to help!