Fish Cloudy Eyes: Common Causes and Treatment

a close up of a fish with the words fish cloudy eyes.

Some fish are more prone to eye issues than others. Fancy goldfish with giant bulbous eyes are the first to come to mind, followed by bettas and koi. What is the cause of “cloudy” eyes and how can you prevent your fish from having permanent issues?

Fish cloudy eye
Koi with cloudy eye

Trauma – The #1 Cause of Fish Cloudy Eyes

Thankfully, humans, cats, dogs, horses and many other species have eyelids to protect their eyes from most serious injury. However, this is not the case with fish. Without eyelids to protect their corneas, a simple abrasion can result in a localized inflammatory reaction. This is the cause of most cloudy eyes in fish. The cornea on the outside of the eye can turn cloudy as the fish’s immune system swims to the rescue. Although you’d think this would be an asymmetrical event, we often see fish with both eyes damaged, but not to the same extent.

Depending on the level of damage, the cloudy eye may be temporary or permanent. Fish with eyeballs bigger than their heads and lots of obstructions in their tanks often suffer from chronic, repeat injuries. If buying a “normal” goldfish isn’t an option, be sure to provide your ocularly-challenged goldfish a soft and obstacle-free environment. Plants specific to bettas, made of soft fabric are the best option.

There is no treatment for traumatic eye injuries in fish. Eye drops are a complete waste of time since they will come off the instant your fish swims away. Providing clean water and a health diet, in addition to removing potential collision, are the best treatment for a traumatic cloudy eye.

Poor Water Quality

The second most common cause of fish cloudy eyes is poor water quality. Yes, one of the signs of chronic stress other than lethargy, decreased appetite, poor immune function and no reaction to Marvin Gaye is decreased healing, so even the smallest abrasion can get serious quickly. Thankfully, this is an easy fix. Fix your water quality and your fish will fix itself!


This seems to be more the case for fish living outside in a pond than indoors in a tank. Suspected increased UV exposure and potential heavy metal contamination increase the likelihood for various cancers. For koi in particular, we see the occasional chromatophoroma run amok. These pigment cell tumors are usually fairly benign, but if they root on the eye, a fish may feel them drag when they swim and try to knock them off. Not only do they cause a cloudy eye, they can cause serious neurologic trauma if they work hard enough.

For benign masses, we usually don’t treat them unless they are cause the fish discomfort. If they are seen trying to scratch their eye out, its time for the eye to go. This is a very safe procedure and we’ve actually done both eyes on one fish!


Issues with fish cloudy eyes can also be a dietary issue. We usually see this present in finicky eaters that only want one food source, and it’s not complete. We know that some fish just won’t cooperate with the menu, but try to do your best to feed them a complete diet. You may have to be a little creative or try out various brands. Just like you have that one brand of peanut butter you just can’t live without, your fish may be the same.

How to treat fish cloudy eye(s)

  1. Check your water quality
  2. Evaluate your fishes’ environment for sources of trauma
  3. Evaluate your fishes’ diet
  4. Still unknown? Contact your local aquatic veterinarian.

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14 thoughts on “Fish Cloudy Eyes: Common Causes and Treatment”

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  4. Hi I have a Gourami that is approx 18mo I got it from a local hobbyist.
    One pupil has turned white. The iris and cornea are normal.
    I’m not sure what is wrong.
    Nitrates climb to 30ppm but I change it regularly. They are fed a variety of suitable foods
    Only one fish has this issue

    Any thoughts what it could be?

  5. My Oscar fish has lost the blackness of its eye. That fish does not react to visual things. What could be the reason for that?

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  8. I have a Betta Fish in my house. I don’t know how old he is but I’ve had him for about 6 months now. I’ve only been feeding him 1type of food: Freeze Dried Bloodworms. I got him from a pet store. One day, I saw on his left eye that he had a cloudy eye and was staying in one corner of the tank for long periods of time and would only move to eat his food. I changed the water of his tank and his left eye was actually getting better. Should I just wait or should I do something else to help his eye? He lives in a 1-gallon tank for now.

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