Why Does My Angelfish Have Red Eyes? (Causes & Solutions)

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A few months ago, I woke up to find my angelfish with a strange shade in its eyes. It seemed like they were turning red for no apparent reason.

As I investigated this topic further, I realized that there are several reasons that might have caused it, and that in some cases, it could be normal.

Why do angelfish develop red eyes? Does it mean they are sick? How can you tell if it’s a natural and genetic trait? And what should you do about it?

In this article, I’ll answer all these questions and more, so you’ll leave with all the information you need. Let’s dive right into it.

Also Read: Facts About Angelfish

Why Are My Angelfish’s Eyes Red?

There are several reasons why your angelfish might have developed red eyes. Here’s what you should know:

1. Bacterial Infection

Bacterial infections in angelfish can cause red eyes, often due to weakened immunity from stress or suboptimal tank conditions.

  • Inflammation Impact: Bacterial presence triggers inflammation, leading to capillary expansion and eye redness, similar to human conjunctivitis.
  • Blood Vessel Reaction: As bacteria multiply, eye blood vessels dilate visibly, intensifying the red hue, a response akin to human eye infections.
  • Other Signs: Alongside red eyes, look for symptoms like fin deterioration or white patches on the body, indicative of systemic bacterial infection.

2. Poor Water Quality

Poor water quality is a primary cause of red eyes in angelfish, typically due to imbalances in chemicals like ammonia or improper pH levels.

  • Chemical Irritants: Elevated ammonia (above 0 ppm) or nitrite levels irritate delicate eye tissues, leading to redness and potential swelling.
  • Stress Induced Redness: Chronic exposure to suboptimal water (pH outside 6.8-7.8) stresses the fish, causing a physiological red-eye response.
  • Other Symptoms: Observe for rapid gill movement or faded colors, common signs of stress from poor water quality in angelfish.

3. Physical Injury

Physical injuries, from collisions with sharp tank decor or conflicts with tankmates, often result in red eyes in angelfish.

  • Trauma Impact: Direct impact to the eye can cause capillary breakage, leading to redness and swelling, similar to a bruise in humans.
  • Infection Risk: Open wounds near the eye can become infected, exacerbating redness and leading to additional eye tissue damage.
  • Other Indicators: Check for torn fins or scratches on the body, indicating potential physical altercations or hazardous tank conditions.

4. Parasitic Infection

Parasitic infections, such as those caused by Ichthyophthirius multifiliis or flukes, can lead to red eyes in angelfish.

  • Parasite Activity: Parasites like Ich (white spot disease) irritate or invade eye tissues, causing inflammation, redness, and sometimes a cloudy appearance.
  • Immune Response: The fish’s immune reaction to parasites, including increased blood flow to infected areas, contributes to eye redness and swelling.
  • Other Clues: Look for white spots (Ich), excessive mucus, or erratic swimming, typical signs of parasitic infestation in angelfish.

5. Stress

Stress in angelfish, often due to environmental factors or social interactions, can lead to red eyes as a physiological response.

  • Stress Response: Stress triggers a release of cortisol, leading to increased blood flow to the eyes and redness, akin to human stress responses.
  • Hormonal Imbalance: Chronic stress causes hormonal imbalances, exacerbating blood vessel dilation and intensifying eye redness.
  • Other Signs: Look for erratic swimming, hiding behavior, or loss of appetite, which are common stress indicators in angelfish.

Also Read: Signs Your Angelfish Is Dying

6. Ammonia Poisoning

Ammonia poisoning, a critical issue in poorly maintained tanks, can cause red eyes in angelfish due to its toxic effects.

  • Toxic Reaction: High ammonia levels (above 0.25 ppm) directly irritate eye tissues, causing redness and potential inflammation.
  • Oxygen Deprivation: Ammonia toxicity can reduce oxygen carrying capacity in blood, leading to oxygen deprivation and red eyes as a distress signal.
  • Other Symptoms: Signs like labored breathing, lethargy, or clamped fins are indicative of ammonia poisoning in angelfish.

7. Natural Red Eyes

It’s not uncommon for some angelfish to naturally have red eyes, a characteristic that is purely genetic and not a sign of any health issue.

  • Genetic Trait: In specific angelfish varieties, red eyes are a natural, hereditary feature, with no connection to health problems. This trait is particularly prevalent in certain selectively bred species.
  • Breed Specificity: Angelfish varieties such as Koi and some strains of Scalare angelfish are known to commonly exhibit naturally occurring red eyes, distinguishing them as a breed characteristic.
  • Healthy Indicators: If the angelfish is active, maintains a good appetite, and shows no signs of stress or illness, then red eyes in these specific breeds can be considered a normal, healthy trait.

What to Do If My Angelfish’s Eyes Are Turning Red?

Here’s what you should do if your angelfish has developed reddish eyes:

1. Antibacterial Medication

When red eyes in angelfish are due to bacterial infections, administering antibacterial medication is crucial.

These medications target the harmful bacteria while safeguarding the fish’s overall health.

  • Medication Selection: Choose a broad-spectrum antibacterial medication like Maracyn or Tetracycline, effective against a range of bacterial infections.
  • Dosage and Duration: Follow the manufacturer’s guidelines for dosage, usually involving treatment for 5-7 days to ensure full bacterial eradication.
  • Isolation of Affected Fish: If possible, isolate the affected fish in a hospital tank to prevent the spread of infection and monitor treatment efficacy.
  • Post-Treatment Care: After completing treatment, change water partially to remove residual medication and reduce chances of antibiotic resistance.

2. Water Quality Improvement

Improving water quality is vital in preventing and treating red eyes caused by environmental stressors. Regular maintenance and monitoring of water parameters are essential.

  • Regular Water Changes: Perform 25-30% weekly water changes to keep the water clean and reduce harmful chemicals like ammonia and nitrites.
  • Monitoring Water Parameters: Use a reliable test kit to monitor pH, ammonia, nitrite, and nitrate levels, keeping them within safe ranges (pH 6.8-7.8, ammonia and nitrite at 0 ppm).
  • Adequate Filtration: Ensure the tank has a robust filtration system that suits its size and bioload, helping maintain stable water conditions.
  • Stress Reducers: Consider adding aquarium-safe stress coat products that help protect the fish’s slime coat and reduce stress. I personally use this API Stress Coat (link to Amazon).

3. Wound Care and Aquarium Salt

If the red eyes are due to physical injury, wound care and the use of aquarium salt can be beneficial. Aquarium salt helps in healing and reducing swelling.

  • Salt Addition: Add aquarium salt at a ratio of 1 tablespoon per 5 gallons of water, which helps reduce swelling and promotes healing.
  • Gentle Water Flow: Adjust the aquarium’s water flow to be gentler, reducing stress on the injured fish and aiding in recovery.
  • Avoid Overcrowding: Ensure the tank isn’t overcrowded to prevent further injuries and stress, providing ample space for all fish.
  • Tank Decor Safety: Inspect and modify tank decorations to remove sharp edges or objects that could cause injury to the fish.

4. Anti-Parasitic Treatment

In cases where red eyes are caused by parasitic infections, administering anti-parasitic treatment is necessary.

These treatments are designed to eliminate parasites without harming the fish.

  • Treatment Choice: Select an effective anti-parasitic medication like Praziquantel or Coppersafe (link to Amazon), targeting common parasites in angelfish.
  • Treatment Application: Follow the specific instructions for the chosen medication, usually involving a treatment period of several days to a week.
  • Water Condition Maintenance: During treatment, maintain optimal water conditions to support the fish’s immune system and enhance treatment effectiveness.
  • Observation Post-Treatment: After treatment, closely observe the fish for any remaining signs of parasitic activity and consider a second treatment cycle if necessary.

Also Read: Angelfish Diseases

5. Eliminating Ammonia

Addressing ammonia levels is crucial if red eyes in angelfish are caused by ammonia poisoning. Ammonia is highly toxic to fish and needs to be eliminated swiftly and effectively.

  • Immediate Water Change: Conduct a 50-70% water change immediately upon detecting high ammonia levels to rapidly reduce its concentration.
  • Ammonia Detoxifiers: Use ammonia detoxifying products like Seachem Prime (link to Amazon) or API Ammo Lock (link to Amazon), which neutralize ammonia without harming fish.
  • Enhanced Filtration: Upgrade or optimize your filtration system, ensuring it is capable of handling the tank’s bioload and efficiently processing waste.
  • Regular Testing: Regularly test the water using ammonia test kits, aiming to maintain ammonia levels at 0 ppm to prevent future issues.

Also Read: Angelfish Water Parameters

6. Stress Reduction Measures

Reducing stress is crucial in preventing and treating red eyes in angelfish, as stress can exacerbate many health issues.

  • Stable Environment: Maintain a stable tank environment with consistent temperature (78-82°F), pH levels (6.8-7.8), and minimal noise or disturbance.
  • Adequate Hiding Spaces: Provide plenty of hiding spaces like plants, caves, or decorations, allowing angelfish to feel secure and reduce stress.
  • Balanced Diet: Feed a high-quality, varied diet appropriate for angelfish, ensuring they receive all necessary nutrients and maintain a healthy immune system.
  • Proper Tank Mates: Carefully select compatible tank mates to prevent aggression or bullying, which can significantly stress your angelfish.

For example, here are some suitable tank mates for angelfish:

  • Neon Tetras
  • Corydoras Catfish
  • Gouramis (e.g., Dwarf Gourami)
  • Harlequin Rasboras
  • Bolivian Ram Cichlids
  • Swordtails
  • Rummy Nose Tetras

On the other hand, I would avoid species like:

  • Betta Fish
  • Tiger Barbs
  • Serpae Tetras
  • African Cichlids
  • Silver Dollar Fish
  • Oscars
  • Convict Cichlids

Also Read: Angelfish Tank Mates

Rummy Nose Tetra

How Do You Know if a Fish’s Eyes Are Bad?

Determining if a fish’s eyes are bad involves observing for changes in appearance and behavior.

Signs like cloudiness, swelling, or the fish rubbing its eyes against objects are key indicators.

  • Cloudiness: Cloudy eyes often indicate a bacterial infection or poor water quality, presenting as a whitish film over the eye.
  • Swelling or Bulging: Swollen or bulging eyes, a condition known as exophthalmia, can result from bacterial infections or water quality issues.
  • Rubbing Eyes: If a fish frequently rubs its eyes against tank decorations, this could signify irritation or an attempt to dislodge parasites.
  • Sudden Loss of Vision: Fish bumping into tank objects or having difficulty locating food might indicate vision loss due to eye health issues.

What Fish Have Red Eyes?

Certain fish species naturally possess red eyes, which is a unique and often breed-specific trait. These red eyes are not indicative of any health issue but rather a genetic characteristic.

  • Albino Varieties: Many albino fish species, like albino Oscars or albino Corydoras, naturally have red eyes due to the lack of pigmentation.
  • Koi Angelfish: Koi Angelfish, a popular aquarium fish, often exhibit bright red eyes as a distinct feature of their coloration.
  • Freshwater Sharks: Some freshwater sharks, like the Rainbow Shark, have a natural red eye coloring that contrasts with their dark bodies.
  • Certain Tetras: Many tetra species, such as the Serpae Tetra, are known for their vibrant red eyes, adding to their visual appeal.
  • Rare Guppy Strains: Some unique strains of guppies have been bred to have red eyes, making them a distinctive choice for aquarium enthusiasts.

What Color Are Angelfish Eyes?

Angelfish typically have eyes that range in color from clear to slightly pigmented, usually reflecting shades of silver or gray.

However, some angelfish varieties, like Koi Angelfish, can naturally exhibit red or orange eyes as a result of selective breeding.

It’s important to note that any sudden change in eye color, such as redness or cloudiness, could indicate health issues and should be monitored closely.

Also Read: Can Angelfish Live In Cold Water?


For quick readers, here’s a short summary:

  • Angelfish may develop red eyes due to bacterial infections, often resulting from stress or poor tank conditions, which cause inflammation and capillary expansion.
  • Poor water quality, characterized by high levels of ammonia or improper pH, is a primary cause of red eyes in angelfish, leading to irritation and stress-induced redness.
  • Physical injuries from tank decor or conflicts can result in red eyes in angelfish, with trauma leading to capillary breakage and potential infection.
  • Parasitic infections, like those from Ichthyophthirius multifiliis, cause eye inflammation and redness in angelfish, with immune response contributing to the condition.
  • Some angelfish naturally have red eyes as a genetic trait, especially in certain breeds like Koi and Scalare, and this is not indicative of any health issue.