Stress In Angelfish: 17 Symptoms And Solutions

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Angelfish are popular in home aquariums because they are calm and easy to take care of. 

However, like all fish, angelfish can sometimes get stressed, and figuring out why can be a bit tricky. That’s why I’ve made this handy guide.

Based on my experience with angelfish, I’ve noticed they are sensitive to changes in their environment. This inspired me to share what I know.

In this article, I’ll walk you through 17 common signs that your angelfish might be stressed and give you practical solutions for each problem.

Let’s dive in and make sure our fishy friends stay happy and healthy.

Also Read: Angelfish Care Guide

My Equipment

Before we begin, here’s a list of the equipment I use in my angelfish aquarium to create a cozy and peaceful environment:

17 Stress Signs in Angelfish

Here are the most common stress symptoms in angelfish:

1. Loss of Appetite

Angelfish experiencing stress often show a reduced interest in food.

This can be due to environmental stressors, illness, or psychological factors. Regular monitoring of their eating habits is essential for their well-being.

How to Treat:

  • Adjust Diet: Introduce a mix of brine shrimp, bloodworms, and high-quality flakes or pellets, rotating daily to encourage interest in eating.
  • Regular Feeding Schedule: Feed small, consistent portions twice a day, preferably in the morning and evening, to establish a reliable routine.
  • Check Water Quality: Regularly test water parameters; maintain a pH of 6.8-7.8, ammonia and nitrite at 0 ppm, and nitrate below 20 ppm.
  • Reduce Tank Stress: Keep the tank environment calm, with dim lighting and minimal noise, to create a peaceful atmosphere for feeding.

Also Read: Why Is My Angelfish Not Eating?

2. Reduced Activity

When stressed, angelfish may become lethargic and show less interest in swimming around the tank.

This change in behavior can indicate discomfort or a health issue. Observing their normal activity levels is vital for early detection of stress.

How to Treat:

  • Optimize Tank Environment: Maintain a stable water temperature between 76-82°F and provide ample hiding spaces with plants or decor.
  • Regular Water Changes: Perform 25% water changes weekly to keep the environment clean and stable, which can encourage more activity.
  • Monitor Tank Mates: Ensure compatibility among fish to avoid aggression or bullying, which can cause stress and reduce activity.
  • Provide Stimulation: Introduce new aquarium decorations or rearrange existing ones periodically to stimulate exploration and activity.

Also Read: Why Is My Angelfish Not Moving?

3. Hiding

Frequent hiding is a common stress response in angelfish.

It often indicates discomfort with their environment or the presence of aggressive tank mates. Continuous hiding can affect their health and stress levels.

How to Treat:

  • Create Safe Zones: Arrange plants, rocks, or caves to provide secure hiding spots, allowing the fish to retreat when needed.
  • Assess Tank Dynamics: Observe interactions with tank mates; remove or separate aggressive fish to reduce stress and encourage more visibility.
  • Control Lighting: Use subdued lighting and avoid sudden changes in light intensity to create a comfortable environment for the angelfish.
  • Limit Disturbances: Keep the area around the aquarium tranquil, avoiding loud noises or frequent movement that can startle the fish.

Also Read: Why Do Angelfish Hide?

4. Erratic Swimming

Erratic swimming, like darting or rubbing against objects, can indicate stress or health issues in angelfish.

This behavior can stem from poor water quality, parasites, or environmental stressors. It’s essential to observe these signs closely for timely intervention.

How to Treat:

  • Check Water Quality: Test for ammonia, nitrites, and nitrates regularly, striving for ammonia and nitrite at 0 ppm, and nitrate below 20 ppm.
  • Inspect for Parasites: Look for signs of parasites or illness, such as white spots or frayed fins, and treat accordingly with appropriate medication, such as the Fritz Mardel Coppersafe (link to Amazon).
  • Ensure Adequate Space: Provide a spacious tank (at least 20 gallons for a pair) to allow sufficient swimming room and reduce stress.
  • Reduce Flow Rate: Adjust the filter’s flow rate to a moderate level to prevent strong currents that can cause erratic swimming.

Also Read: Angelfish Swimming Erratically

5. Gasping

Gasping at the water’s surface often indicates oxygen deficiency or poor water quality. 

Angelfish may gasp due to overcrowded tanks, high ammonia levels, or insufficient aeration. This behavior needs immediate attention to prevent serious health issues.

How to Treat:

  • Increase Aeration: Use an air stone or a more powerful filter to enhance oxygen levels in the tank, ensuring a steady flow of bubbles.
  • Reduce Tank Stocking: Keep the number of fish appropriate for the tank size; generally, 1 inch of fish per gallon of water is a good rule.
  • Regular Water Testing: Test for ammonia and nitrites regularly, keeping both as low as possible.
  • Maintain Cleanliness: Perform regular water changes (25% weekly) and clean the substrate to remove waste and uneaten food, improving water quality.

Also Read: Angelfish Gasping For Air

6. Breathing Fast

Angelfish breathing rapidly can signal stress from environmental factors or health issues.

It’s a critical symptom that needs immediate attention, as it can be a sign of poor water quality or disease. Observing their breathing rate and other behaviors is vital.

How to Treat:

  • Enhance Oxygenation: Use an air pump or air stone to increase oxygen levels in the water, which can help normalize breathing rates.
  • Temperature Regulation: Ensure the water temperature is stable within 76-82°F, as extreme temperatures can affect respiratory rates.
  • Disease Check: Look for signs of infections or parasites, such as spots or erratic swimming, and treat with specific aquarium medications.
  • Stress Reduction: Create a peaceful environment, avoiding sudden changes in light or noise, to help reduce stress-induced rapid breathing.

Also Read: Angelfish Breathing Fast

7. Staying at the Top

Angelfish staying near the water’s surface might indicate oxygen scarcity or health issues. 

This behavior requires careful monitoring, as it can be due to various environmental or health-related factors.

How to Treat:

  • Improve Aeration: Ensure the tank has sufficient aeration, possibly by upgrading the filtration system for better water movement and oxygen distribution.
  • Alleviate Overcrowding: Reduce the number of fish if the tank is overcrowded, as this can deplete oxygen levels and cause stress.
  • Examine Water Parameters: Apart from ammonia and nitrites, ensure the tank’s pH is within the ideal range of 6.8-7.8 for angelfish.
  • Health Evaluation: Regularly observe for any signs of illness, like lethargy or lack of appetite, and seek veterinary advice if needed.

Also Read: Angelfish Staying At The Top

8. Staying at the Bottom

If angelfish are frequently found at the bottom, it could signal discomfort, stress, or health issues. This behavior requires assessment of environmental and social factors in the tank.

How to Treat:

  • Environmental Comfort: Make sure the tank has varied topography with plants and hiding spots, allowing the fish to feel secure at the bottom.
  • Social Dynamics Check: Observe interactions with tank mates to identify any bullying or territorial disputes, and intervene if necessary.
  • Lighting Adjustment: Ensure the lighting in the tank is not too intense, as bright lights can sometimes cause fish to seek shelter at the bottom.
  • Health Inspection: Look for physical signs of illness or stress, such as clamped fins or faded colors, and consult a vet for fish-specific advice.

Also Read: Angelfish Sitting At The Bottom

9. Aggressive Behavior

Aggression in angelfish, such as chasing or nipping, is often a response to stress, territorial issues, or breeding behaviors. It’s important to distinguish the cause to effectively manage it.

How to Treat:

  • Tank Size and Layout: Provide a spacious tank, ideally 20 gallons for a pair, with plenty of hiding spots to diffuse aggressive interactions.
  • Fish Compatibility: Ensure that tank mates are compatible in temperament and size to minimize conflicts and aggressive behavior.
  • Breeding Behavior Monitoring: If aggression is related to breeding, provide a separate breeding tank to reduce stress on other tank inhabitants.
  • Territorial Management: Regularly rearrange tank decorations to prevent any one fish from establishing and defending a territory aggressively.

Also Read: Why Has My Angelfish Become Aggressive?

10. Making Bubbles

Bubble-making in angelfish can be a part of their normal behavior, especially in males constructing nests.

However, if it’s excessive, it might indicate a problem that needs addressing.

How to Treat:

  • Breeding Behavior Assessment: Understand that bubble nest building is natural for males, especially if paired with a female, and does not usually indicate a problem.
  • Environmental Check: Ensure the tank environment, including water temperature and cleanliness, is maintained at optimal conditions for angelfish.
  • Observe Other Behaviors: Look for signs of stress or illness that might accompany unusual bubble-making to determine if it’s a symptom of a larger issue.
  • Tank Maintenance: Regular maintenance, including partial water changes and substrate cleaning, can help maintain a healthy environment reducing the need for stress-related behaviors.

Also Read: Angelfish Making Bubbles

11. Laying on the Side

Angelfish lying on their side is a critical symptom, often indicating severe stress or illness. Immediate action is necessary for their health.

How to Treat:

  • Emergency Health Check: Inspect for symptoms like bloating or sores; if present, isolate the fish in a quarantine tank and consult a fish vet.
  • Water Quality Review: Test for pH (ideal range 6.8-7.8), temperature (76-82°F), and nitrate (keep as low as possible, ideally under 20 ppm).
  • Stress Minimization: Create a calm environment, avoiding loud sounds or bright lights, and ensure the tank is spacious enough for free movement.
  • Recovery Environment: In a quarantine tank, maintain optimal water conditions and monitor the fish for any improvement or further decline.

Also Read: Angelfish Laying On Its Side

12. Twitching

Twitching in angelfish can be a sign of distress, possibly due to parasites or poor water conditions. Immediate investigation and action are needed.

How to Treat:

  • Parasite Examination: Look for signs like white spots; treat with anti-parasitic medication like copper sulfate or praziquantel following dosage instructions.
  • Water Condition Optimization: Perform 30% water changes bi-weekly and ensure the filter is adequate for the tank size to maintain water quality.
  • Stress Reduction Techniques: Keep the tank environment stable with gradual changes in lighting (using timers) and temperature (using reliable heaters).
  • Health Monitoring: Observe the fish for additional symptoms and, if twitching persists, consult with a vet who specializes in fish.

Also Read: Why Is My Angelfish Twitching?

13. Keeping Mouth Open

If an angelfish keeps its mouth open, it could indicate respiratory distress or a physical issue. Quick assessment and action are crucial.

How to Treat:

  • Check for Blockages: Gently examine the mouth for obstructions or injuries using a soft net to handle the fish if necessary.
  • Oxygen Level Adjustment: Increase oxygen by adding an air stone or upgrading the filter, ensuring strong water surface agitation.
  • Water Quality Maintenance: Regularly clean the tank and perform 25% water changes weekly to maintain a clean and healthy environment.
  • Consult a Specialist: If symptoms persist, consult an aquarium specialist or veterinarian for specific advice or treatment.

Also Read: Angelfish’s Mouth Stuck Open

14. Faded Stripes

Faded stripes in angelfish can indicate stress or health issues. Addressing environmental and dietary needs is essential for recovery.

How to Treat:

  • Environment Comfort: Provide hiding places like plants or caves and maintain a consistent light schedule to reduce stress.
  • Nutrition Improvement: Offer a balanced diet of high-quality flakes, frozen brine shrimp, and bloodworms, rotating food types daily.
  • Water Quality Control: Test water weekly, maintaining pH between 6.8-7.8 and temperature at 76-82°F, and perform 25% water changes weekly.
  • Health Assessment: Watch for other illness signs and, if stripe fading continues or worsens, seek advice from a fish health expert.

Also Read: Why Do Angelfish Stripes Fade?

15. Color Loss

Color loss in angelfish can be a sign of stress, poor nutrition, or unsuitable water conditions. 

Prompt identification and correction of the underlying cause are crucial to restore their vibrant colors.

How to Treat:

  • Dietary Enrichment: Feed a varied diet including high-quality pellets, frozen foods like brine shrimp, and occasional vegetable matter to provide essential nutrients.
  • Water Quality Management: Regularly test the water, maintaining a pH between 6.8-7.8 and temperature around 76-82°F, and perform bi-weekly 25% water changes.
  • Stress Reduction: Ensure a peaceful tank environment with adequate space, minimal noise, and consistent lighting to minimize stress.
  • Illness Check: Examine for signs of disease such as lethargy or spots, and consult a vet if color loss is accompanied by other health issues.

Also Read: Angelfish Turning White

16. Turning Black

Angelfish turning black may indicate stress, genetic factors, or a response to environmental changes. It’s important to assess and address any potential stressors or health issues.

How to Treat:

  • Environmental Assessment: Check for any changes in the tank that could cause stress, such as fluctuating temperatures or aggressive tank mates.
  • Nutrition Balance: Provide a balanced diet with a mix of quality flakes, live foods, and vegetables to ensure overall health and coloration.
  • Regular Health Monitoring: Observe the fish for other signs of stress or illness and act promptly to treat any identified problems.
  • Genetic Consideration: Acknowledge that some color changes can be natural, especially in younger angelfish, and may not always indicate a problem.

Also Read: Angelfish Turning Black

17. Stunted Growth

Stunted growth in angelfish can be due to inadequate nutrition, overcrowding, or poor water quality. Addressing these factors is essential for the healthy development of the fish.

How to Treat:

  • Optimal Feeding: Feed high-quality, nutrient-rich foods like specially formulated angelfish pellets and live or frozen foods in appropriate amounts.
  • Tank Space Management: Ensure the tank is adequately sized (20 gallons for a pair) to provide enough space for growth and movement.
  • Water Quality Maintenance: Keep the water clean and well-filtered, performing regular 30% water changes every week to maintain a healthy environment.
  • Growth Tracking: Monitor the growth of the fish regularly and adjust care as needed, including diet and tank conditions, to support healthy development.

Also Read: Why Is My Angelfish Not Growing?

Why Do Angelfish Get Stressed?

Angelfish, like many other aquarium fish, can experience stress due to environmental factors and changes in their habitat.

Stress in angelfish can lead to health problems and changes in behavior, making it crucial to understand and mitigate the causes.

  • Poor Water Quality: Suboptimal water conditions, like high ammonia (over 0 ppm) or fluctuating pH levels, can cause significant stress in angelfish.
  • Overcrowding: A cramped tank, especially smaller than 20 gallons for a pair of angelfish, leads to stress due to limited space and resources.
  • Inadequate Diet: Lack of a varied, nutritious diet can lead to nutritional deficiencies, weakening angelfish and making them prone to stress.
  • Sudden Environmental Changes: Rapid changes in temperature, lighting, or water chemistry can shock angelfish, triggering a stress response.
  • Incompatible Tank Mates: Aggressive or overly active fish can intimidate angelfish, causing stress from constant harassment or fear.

Also Read: Facts About Angelfish

For example, here are some friendly fish species that can be kept with angelfish:

  • Corydoras catfish
  • Neon tetras
  • Bolivian ram cichlids
  • Bristlenose plecos
  • Harlequin rasboras
  • Cardinal tetras
  • Clown loaches

On the other hand, I would avoid aggressive or fast-swimming species that can harass your angelfish, including:

  • Betta fish
  • African cichlids
  • Goldfish
  • Guppies
  • Tiger barbs
  • Oscar fish
  • Red-tailed black sharks

Recognizing Stress vs. Normal Angelfish Behavior

Distinguishing between stressed and normal behavior in angelfish is key to ensuring their well-being.

Stress behaviors often indicate underlying problems, while normal behaviors are part of their everyday life and interaction with the environment.

  • Loss of Appetite vs Eating Habits: A sudden refusal to eat can indicate stress, unlike normal pickiness or fluctuations in appetite with water changes.
  • Hiding vs Resting: Constant hiding, especially in new or bright areas, suggests stress, whereas occasional resting in favorite spots is normal.
  • Erratic Swimming vs Exploration: Frantic or erratic swimming often signals stress, contrasting with normal curious exploration of the tank.
  • Rapid Breathing vs Normal Respiration: Persistently rapid gill movement indicates stress, different from the regular, more relaxed breathing pattern.

What Happens if Angelfish Stress Goes Untreated?

If stress in angelfish goes untreated, it can lead to a weakened immune system, making them more susceptible to diseases and infections.

Chronic stress can also cause behavioral changes, such as aggression or lethargy, and may lead to a decline in overall health, including issues like loss of appetite or color fading. 

Additionally, prolonged stress can shorten the lifespan of the angelfish and affect their ability to breed successfully.

Also Read: Angelfish Diseases

Can Stressed Angelfish Get Better?

Yes, stressed angelfish can recover if the underlying causes of their stress are identified and addressed promptly.

This recovery process involves improving their environment, such as optimizing water quality, providing a balanced diet, and ensuring a peaceful tank with compatible tank mates. 

It’s also crucial to regularly monitor the angelfish for any signs of lingering stress or health issues and continue making adjustments as needed to maintain their well-being.


For quick readers, here’s a short summary:

  • Angelfish can experience stress due to environmental factors and changes in their habitat, leading to health problems and behavioral changes.
  • Recognizing stress in angelfish is key, as it often indicates underlying issues, contrasting with normal behaviors that are part of their everyday life.
  • Untreated stress in angelfish can weaken their immune system, lead to behavioral changes, and shorten their lifespan, affecting their overall health and breeding ability.
  • Stressed angelfish can recover if the causes are identified and addressed, involving improvements in environment, diet, and tank conditions.
  • Addressing angelfish stress involves regular monitoring and adjustments in their environment, diet, and social dynamics within the tank.