Why Is My Angelfish Turning Red? (5 Fast Solutions)

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A few months ago, I noticed that one of my angelfish developed red coloration at the base of its fins. As it turned out, I discovered that there had been an ammonia spike in my fish tank.

What causes angelfish to turn red? Is it always related to ammonia? What else could it be? And, how can you identify the underlying cause?

In this article, I’ll answer all these questions and more, ensuring you leave with all the information you need. Let’s get started.

Why Is My Angelfish Turning Red at the Base of Its Fins?

Angelfish turning red at the base of their fins can be a concerning sign for aquarists. This discoloration is often an indicator of issues within the tank environment.

Let’s delve into the possible reasons behind this:

1. Elevated Ammonia, Nitrites, or Nitrates in Water

Elevated levels of ammonia, nitrites, or nitrates indicate a significant imbalance in the aquarium’s ecosystem, impacting angelfish health.

  • Toxicity of Ammonia: Ammonia is a potent toxin that irritates fish skin, gills, and fins. Even low levels (above 0 ppm) can cause redness and other stress symptoms in angelfish.
  • Nitrite and Nitrate Impact: Elevated nitrites and nitrates, though less toxic than ammonia, can still stress angelfish. Levels above 20 ppm for nitrites and 50 ppm for nitrates are particularly concerning.
  • Sources of Chemicals: Common sources of these harmful chemicals include overfeeding, decaying plant matter, and insufficient tank cleaning, leading to accumulation.

2. Stress or Agitation

Stress in angelfish can be caused by various environmental factors, often resulting in physical symptoms like redness in fins.

  • Aggressive Tank Mates: Incompatible or aggressive tank mates can cause significant stress. Angelfish are territorial and may become stressed in overcrowded or hostile environments.
  • Environmental Changes: Sudden changes in water parameters (like temperature and pH) or disruptive maintenance routines can stress angelfish, leading to physical signs of distress.
  • Lack of Hiding Spaces: A lack of adequate hiding spaces and environmental enrichment in the tank can contribute to stress, manifesting as redness at the fin bases.

3. Poor Water Quality

Poor water quality is a broad term encompassing various factors that can negatively impact the health of angelfish.

  • Organic Waste Accumulation: Excessive organic waste from fish excreta, uneaten food, and decaying plants leads to poor water quality, stressing angelfish and causing redness in fins.
  • Inadequate Filtration: Inefficient filtration systems fail to remove harmful substances, resulting in a buildup of toxins that can irritate and harm angelfish.
  • Lack of Regular Maintenance: Irregular water changes and tank cleaning can lead to a gradual decline in water quality, affecting the health and appearance of angelfish.

4. Fin Rot or Other Infections

Fin rot and other bacterial or fungal infections can cause redness, along with other symptoms, at the fins of angelfish.

  • Symptoms of Fin Rot: Fin rot typically presents as fraying or disintegration of the fin edges, often accompanied by a reddening at the base. It’s usually caused by poor water quality or stress.
  • Bacterial Infections: Bacterial infections can cause inflammation and redness in the fins. These infections are often secondary to stress or injury.
  • Fungal Invasions: Fungal infections might also cause similar symptoms. They typically appear as cottony growths on the fins, alongside redness and irritation at the base.

Also Read: Angelfish Fin Rot

5. Dietary Deficiencies

An inadequate diet can lead to various health issues in angelfish, including changes in fin coloration.

  • Lack of Essential Nutrients: A diet lacking in essential vitamins and minerals can lead to weakened immunity and poor fin health, potentially causing redness at the fin bases.
  • Importance of Varied Diet: Angelfish require a varied diet including proteins, vitamins, and minerals. A monotonous or unbalanced diet can lead to deficiencies affecting fin health.
  • Omega Fatty Acids Role: Omega fatty acids are crucial for healthy fish skin and fins. A deficiency in these can lead to deteriorating fin health, manifested as redness or other abnormalities.

How to Treat Angelfish That Turn Red

Treating angelfish that have turned red at the base of their fins involves addressing the underlying causes. Here’s what you should do:

1. Regular Water Testing and Maintenance

Proper testing and maintenance of water is vital in treating redness in angelfish, as it helps identify and rectify imbalances in the aquarium’s ecosystem.

  • Routine Testing: Test water weekly using a reliable aquarium test kit. Aim for ammonia and nitrite levels at 0 ppm, nitrates below 20 ppm, and a pH between 6.8 and 7.8. I use the API Freshwater Master Test Kit (link to Amazon).
  • Frequent Water Changes: Perform 20-25% water changes weekly. Use a gravel vacuum to remove debris from the substrate, and replace with dechlorinated water that matches the tank’s temperature.
  • Filter Maintenance: Clean and maintain your filter monthly. Replace media as recommended by the manufacturer, ensuring not to disrupt the beneficial bacteria essential for a healthy tank balance.
My API Freshwater Master Test Kit

2. Stress Reduction

Reducing stress is key in treating and preventing redness in angelfish, as stress weakens their immune system and makes them more susceptible to diseases.

  • Adequate Hiding Spaces: Provide plenty of plants, caves, or decorations. These hiding places offer a sense of security, reducing stress and improving overall wellbeing.
  • Stable Environment: Keep a consistent aquarium environment. Avoid rapid changes in lighting, temperature (ideal range: 76-82°F), and water chemistry to minimize stress.
  • Appropriate Tank Mates: Choose compatible tank mates for your angelfish. Avoid aggressive or fin-nipping species, and ensure there’s enough space for all fish to reduce territorial disputes.

On this matter, here are some suitable tank mates for angelfish:

  • Corydoras Catfish (Corydoras spp.)
  • Dwarf Gourami (Trichogaster lalius)
  • Platies (Xiphophorus maculatus)
  • Mollies (Poecilia spp.)
  • Harlequin Rasbora (Trigonostigma heteromorpha)
  • Cardinal Tetra (Paracheirodon axelrodi)
  • Bristlenose Pleco (Ancistrus spp.)

I would avoid species like:

  • Tiger Barbs (Puntigrus tetrazona)
  • Red Tail Shark (Epalzeorhynchos bicolor)
  • Betta Fish (Betta splendens)
  • African Cichlids (Various species within Cichlidae family)
  • Goldfish (Carassius auratus)
  • Jack Dempsey (Rocio octofasciata)
  • Oscars (Astronotus ocellatus)
Jack Dempsey

3. Water Quality Improvement

Improving water quality is essential in treating redness in angelfish, as poor water conditions are a primary cause of stress and disease.

  • Effective Filtration: Use a high-quality filter that suits the size of your aquarium. It should circulate the entire tank volume at least 4-5 times per hour to ensure efficient waste removal. My recommendation: Fluval C4 Power Filter (link to Amazon).
  • Regular Water Testing: Monitor and adjust water parameters regularly. Use conditioners to bind harmful metals and chemicals. I use the Tetra AquaSafe (link to Amazon) whenever I’m doing a water change.
  • Control Feeding: Feed angelfish high-quality food in small amounts twice a day. Overfeeding leads to excess waste, which deteriorates water quality and contributes to health issues.

4. Treat Diseases

Identifying and treating any underlying diseases is crucial in resolving issues like redness in angelfish.

  • Diagnosis and Medication: If a disease like fin rot or bacterial infection is suspected, consult a vet or use over-the-counter fish medications. My recommendation: API FIN & BODY CURE (link to Amazon).
  • Quarantine Affected Fish: To prevent the spread of disease, quarantine affected fish in a separate tank. This also allows for targeted treatment and close monitoring of the sick fish.
  • Maintain Treatment Regimen: Consistently follow the treatment regimen. This may include medication, water changes, and monitoring for improvement or further symptoms.

5. Balanced Diet

A balanced diet is essential for maintaining good health and preventing issues like fin redness due to nutritional deficiencies.

  • Varied Nutritional Intake: Feed angelfish a varied diet comprising high-quality flakes, pellets, frozen or live foods like brine shrimp or bloodworms. This ensures a range of nutrients.
  • Controlled Feeding: Feed small amounts twice daily, only as much as they can consume in three minutes. Overfeeding leads to waste buildup, affecting water quality and health.
  • Supplement with Vitamins: Consider supplements or vitamin-enriched foods to boost immune health. This can be particularly helpful in recovering or stressed fish, improving overall vitality.

Also Read: Angelfish Broken Fins


How Can You Tell If an Angelfish Is Stressed?

Determining if an angelfish is stressed is crucial for maintaining their health and well-being. There are several signs, besides turning red, that can indicate stress in these fish.

  • Erratic Swimming: A stressed angelfish may swim erratically or atypically fast. This behavior, often looking panicked or directionless, indicates discomfort or fear in the tank environment.
  • Loss of Appetite: When stressed, angelfish might show a reduced interest in food or stop eating altogether. A healthy angelfish is typically eager to eat, so changes in feeding habits can be a sign of stress.
  • Hiding Excessively: While occasional hiding is normal, continuous hiding or avoiding coming out even during feeding is a stress symptom. It often suggests discomfort or fear caused by the tank environment or tank mates.
  • Clamped Fins: Angelfish displaying clamped fins, where fins are held unusually close to the body, are likely experiencing stress. This posture is a clear departure from their normal, relaxed fin positioning.

Why Is My Angelfish’s Mouth Turning Red?

Redness around an angelfish’s mouth can be a sign of bacterial infection or injury.

This can be caused by factors like aggressive tank mates, rough tank decorations, or poor water quality.


  • Improve Tank Environment: Separate aggressive tank mates and cover sharp tank decorations with aquarium-safe silicone. Ideal tank size for angelfish is 20 gallons or more.
  • Enhance Water Quality: Conduct weekly 20-25% water changes, use a water testing kit to check pH, ammonia, nitrites, and nitrates, maintaining ammonia and nitrite levels at 0 ppm.
  • Diet and Stress Reduction: Feed high-quality, varied diet to boost immunity and keep the tank well-planted to provide hiding spaces, reducing stress.

Why Does My Angelfish Have Red Eyes?

Red eyes in angelfish can indicate stress, poor water quality, or a potential eye infection. 

Stress can be caused by overcrowding, incompatible tank mates, or sudden changes in the tank environment.


  • Optimize Tank Conditions: Ensure a minimum of 5 gallons per angelfish, provide dim lighting for 8-10 hours a day to mimic natural conditions, and maintain a stable temperature between 76-82°F.
  • Regular Health Checks: Perform weekly water quality tests, and if eye infection is suspected, use antibiotic treatments or eye drops recommended by a vet.
  • Stress Management: Avoid sudden changes in the tank, such as abrupt lighting changes or temperature fluctuations, and provide hiding places like plants or caves.

What Are the Red Spots on My Angelfish?

Red spots on an angelfish are often symptoms of bacterial infections, such as hemorrhagic septicemia, or a reaction to poor water quality.

These spots can also arise from physical injuries or parasitic infections.


  • Maintain Water Quality: Perform 25-30% weekly water changes, use water conditioners to neutralize harmful chemicals, and ensure the temperature stays between 76-82°F.
  • Balanced Diet and Environment: Offer a diet rich in vitamins and minerals, and provide a stress-free environment with plenty of hiding spaces and minimal loud noises or vibrations near the tank.
  • Consult a Fish Specialist: If red spots persist or worsen, seek advice from a fish specialist for possible antibiotic treatment or other specific medications.


For quick readers, here’s a short summary:

  • Angelfish turning red at the base of their fins is commonly due to high levels of ammonia, nitrites, or nitrates in the water, indicating an imbalance in the tank’s ecosystem.
  • Stress from aggressive tank mates, environmental changes, or lack of hiding spaces can cause physical symptoms like redness in angelfish fins.
  • Poor water quality, resulting from organic waste accumulation, inadequate filtration, or irregular maintenance, can lead to redness and stress in angelfish.
  • Redness at the base of angelfish fins may be a sign of fin rot or other infections, often linked to poor water quality or stress.
  • Dietary deficiencies, particularly in essential nutrients and omega fatty acids, can weaken angelfish immunity and lead to changes in fin coloration, including redness.