Why Is My Angelfish Swimming Erratically? (5 Easy Solutions)

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Angelfish are strong and hardy, which is one reason why lots of people who like fish choose them. They look beautiful and do interesting things.

But, they can be tricky to take care of sometimes. I remember when one of my angelfish was swimming erratically and seemed uncomfortable. It was really concerning.

Luckily, after some good research, I figured out how to fix the problem. Now, I’m going to show you the steps to help if you see something similar. Let’s get started.

Is Erratic Swimming in Angelfish Normal?

No, erratic swimming in angelfish is not normal. This behavior is often a sign of stress, poor water quality, or illness.

It’s important to check water parameters, look for signs of disease, and ensure a stress-free environment to address the issue.

Why Is My Angelfish Swimming Erratically?

There are a couple of reasons your angelfish might be swimming in this manner. Let me explain:

1. Water Quality Issues

Unstable water conditions are a leading cause of unusual swimming behaviors in angelfish, including erratic movements.

  • Toxic Buildup: High ammonia and nitrite levels (ideally at 0 ppm) and nitrates above 20 ppm can stress fish, resulting in unpredictable swimming.
  • pH Fluctuations: Angelfish prefer a stable pH between 6.8 and 7.8; sudden shifts can lead to disoriented and irregular swimming.
  • Identification Tip: Signs like gasping at the water’s surface or faded colors can indicate water quality problems.

2. Parasitic Infections

Parasites can cause significant health issues in angelfish, manifesting in abnormal swimming patterns.

  • Direct Impact: Parasites such as Ich or flukes attach to fish, causing discomfort and erratic, jerky movements as the fish tries to dislodge them.
  • Secondary Symptoms: Infected fish may exhibit flashing (rubbing against objects) along with irregular swimming.
  • Identification Tip: White spots (Ich) or excessive mucus are indicators of parasitic infection.

3. Bacterial Diseases

Bacterial infections can compromise an angelfish’s bodily functions, leading to erratic swimming behavior.

  • Systemic Effects: Infections impacting the swim bladder can cause buoyancy issues, resulting in unstable swimming.
  • Behavioral Changes: Fish with infections often show lethargy or appetite loss in addition to unusual swimming.
  • Identification Tip: Look for ulcers, red streaks, or swollen eyes as signs of bacterial infection.

4. Stress or Environmental Factors

Angelfish are sensitive to their surroundings, and stress can lead to unpredictable swimming patterns.

  • Environmental Changes: Abrupt changes in lighting, water flow, or tank mates can cause stress, leading to inconsistent swimming.
  • Crowded Conditions: Overcrowding can lead to stress and territorial disputes, evident in erratic swimming.
  • Identification Tip: Signs like hiding, reduced eating, or aggression towards other fish suggest stress.

Also Read: Stress In Angelfish

5. Nutritional Deficiencies

An inadequate diet can negatively impact an angelfish’s health, leading to erratic swimming behaviors.

  • Lack of Essential Nutrients: A deficiency in vital vitamins and minerals can weaken muscles, causing unstable swimming.
  • Improper Diet: Feeding low-quality or monotonous diets can result in nutritional imbalances, affecting swimming.
  • Identification Tip: Indicators like color fading or thinning indicate possible nutritional deficiencies.

How to Treat Angelfish That Swim Erratically

To assist an angelfish that’s darting around, just follow these guidelines:

1. Improving Water Quality and Regular Maintenance

Proper water quality is vital for angelfish exhibiting erratic swimming. This includes systematic water changes, filter care, and monitoring of water parameters.

  • Regular Water Changes: Perform 25-30% weekly water changes with a siphon to remove debris and waste, ensuring ammonia and nitrites stay at 0 ppm and nitrates below 20 ppm. I recommend the Laifoo Aquarium Siphon (link to Amazon).
  • Filter Maintenance: Clean or replace filter media every 3-4 weeks, ensuring efficient waste removal and optimal water flow, which is crucial for a healthy tank environment.
  • Testing Water Regularly: Use water test kits weekly to ensure ammonia and nitrites are at 0 ppm and nitrates stay below 20 ppm, adjusting as necessary.
  • Temperature Control: Keep water temperature steady between 76-82°F, using an aquarium heater and regularly checking with a thermometer to prevent stress from temperature fluctuations.

Also Read: Angelfish Water Parameters

2. Treating Parasitic Infections with Appropriate Medications

Effective treatment of parasitic infections in angelfish involves specific medications and careful tank management.

  • Medication Use: Apply anti-parasitic treatments like copper sulfate or malachite green as per instructions, usually dosing 2-3 ml per 10 gallons of water. I found the Fritz Mardel Coppersafe (link to Amazon) to be extremely useful.
  • Quarantine Infected Fish: Isolate affected fish in a quarantine tank during treatment to prevent spreading, using a separate tank of at least 10-20 gallons.
  • Water Changes During Treatment: Perform 15-20% water changes before each medication dose to remove parasites and medicine residues, enhancing treatment effectiveness.
  • Monitoring Progress: Regularly observe the fish for symptom improvement throughout the treatment duration, which typically lasts 5-10 days.

3. Addressing Bacterial Diseases with Antibiotics

Bacterial diseases in angelfish require targeted antibiotic treatments and attentive care.

  • Antibiotic Treatment: Administer antibiotics such as erythromycin or tetracycline, typically dosing 250-500 mg per 20 gallons of water. You can also use over-the-counter products like the Seachem PolyGuard (link to Amazon).
  • Quarantine for Treatment: Place sick fish in a separate quarantine tank, ideally 10-20 gallons, during antibiotic treatment to reduce stress and prevent disease spread.
  • Water Quality During Antibiotic Use: Conduct 10-15% water changes before each antibiotic dose to maintain water quality and remove residual medication.
  • Observing Recovery: Monitor the fish daily for signs of recovery, which usually becomes noticeable within 5-7 days of starting treatment.

Also Read: Angelfish Diseases

4. Reducing Stress through Environmental Adjustments

Minimizing stress is key in treating angelfish with erratic swimming.

  • Stable Environment: Ensure consistent water parameters and a quiet, stable environment; sudden changes can exacerbate stress-related behaviors.
  • Adequate Space: Provide enough space for each angelfish, ideally 10 gallons per fish, to reduce territorial stress and promote healthier swimming patterns.
  • Shelter and Hiding Places: Add plants, rocks, or decorations to create hiding places, offering a sense of security and reducing stress in the aquarium.
  • Appropriate Tank Mates: Choose compatible tank mates to prevent aggression; avoid overly active or aggressive species that can stress angelfish.

For instance, here are some calm fish that can live peacefully with angelfish:

  • Neon Tetra (Paracheirodon innesi)
  • Harlequin Rasbora (Trigonostigma heteromorpha)
  • Corydoras Catfish (Corydoras spp.)
  • Bolivian Ram (Mikrogeophagus altispinosus)
  • Gourami (Trichogaster spp.)
  • Cardinal Tetra (Paracheirodon axelrodi)
  • Honey Gourami (Trichogaster chuna)

However, aggressive fish that usually can’t coexist with angelfish include:

  • Oscar (Astronotus ocellatus)
  • Jack Dempsey Cichlid (Rocio octofasciata)
  • Red Devil Cichlid (Amphilophus labiatus)
  • Green Terror (Andinoacara rivulatus)
  • African Cichlids (Various species from the Cichlidae family)
  • Tiger Oscar (Astronotus ocellatus ‘Tiger’)
  • Flowerhorn Cichlid (Hybrid cichlid, various varieties)

Also Read: Angelfish Tank Mates

5. Ensuring Balanced Nutrition and Dietary Supplements

Proper nutrition is crucial for the overall health and behavior of angelfish.

  • Varied Diet: Feed a mix of high-quality flakes, pellets, and frozen or live foods like brine shrimp or bloodworms to provide a balanced diet.
  • Regular Feeding Schedule: Feed angelfish 2-3 times daily, offering only as much food as they can consume in 3 minutes to prevent overfeeding.
  • Nutritional Supplements: Incorporate vitamin and mineral supplements, especially for fish feeding predominantly on dry foods, to ensure comprehensive nutrition. My recommendation: Seachem Nourish (link to Amazon).
  • Observing Eating Habits: Monitor the fish’s appetite and eating behavior; a healthy angelfish should be eager to eat and display vibrant colors.

Also Read: How To Feed Angelfish

Other Signs Indicating Your Angelfish Is Stressed

Angelfish exhibit several signs when they are stressed, beyond erratic swimming.

These behaviors or physical changes are indicators that the fish is not comfortable in its environment.

  • Loss of Appetite: A stressed angelfish may eat less or refuse food altogether, a significant change from its usual eager feeding behavior.
  • Faded Colors: Stress can cause an angelfish’s colors to become dull or faded, rather than their normal vibrant hues.
  • Hiding Behavior: Frequent hiding or reluctance to come out, especially in a normally active fish, can indicate stress or discomfort.
  • Increased Respiration: Rapid gill movement or gasping at the water’s surface suggests the fish is stressed and struggling with water quality or oxygen levels.

Also Read: Why Is My Angelfish Twitching?

Why Is My Angelfish Darting Around After a Water Change?

Angelfish darting after a water change is often due to abrupt changes in water conditions. This behavior indicates stress from the new environment in their tank.

  • Temperature Shock: Match the new water’s temperature within 2°F of the tank’s to prevent temperature shock, using a thermometer for accuracy.
  • Chemical Imbalance: Use a water conditioner to neutralize chlorine and match the pH of new water to the tank, preventing chemical stress.
  • Disrupted Environment: Add water gently to minimize disturbance and keep the tank’s layout consistent during water changes.
  • Oxygen Levels: Ensure the new water is oxygenated by aerating it before adding, or use an air stone to maintain oxygen levels.

How to Prevent Angelfish from Swimming Erratically in the Future?

Preventing erratic swimming in angelfish involves maintaining stable water conditions and a stress-free environment. Regular monitoring and careful adjustments are key.

  • Stable Water Parameters: Regularly test and adjust water parameters, keeping ammonia and nitrites at 0 ppm and nitrates below 20 ppm.
  • Consistent Water Changes: Perform 20-25% water changes weekly, using a gravel vacuum to maintain cleanliness without drastic environmental changes.
  • Stress-Free Environment: Create a calm environment with proper hiding spaces and compatible tank mates, avoiding overcrowded conditions.
  • Balanced Diet: Feed a variety of high-quality foods, providing all necessary nutrients and maintaining a regular feeding schedule.

Also Read: Angelfish’s Mouth Stuck Open


For quick readers, here’s a short summary:

  • Erratic swimming in angelfish indicates stress, poor water quality, or illness; monitoring water parameters and providing a stress-free environment are essential.
  • Causes include water quality issues, parasitic infections, bacterial diseases, environmental stress, and nutritional deficiencies, each requiring specific attention.
  • Treatments involve improving water quality, addressing parasitic and bacterial infections with appropriate medications, reducing environmental stress, and ensuring balanced nutrition.
  • After a water change, angelfish may dart due to abrupt changes in conditions; it’s crucial to match temperature, address chemical imbalances, and minimize disruption.
  • Preventing erratic swimming in the future requires maintaining stable water conditions, regular water changes, a stress-free environment, and a balanced diet.