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Why Is My Angelfish Not Growing? (5 Practical Solutions)

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A few years ago, my dad started taking care of a pair of young Angelfish. At first, everything seemed fine, but then we noticed something strange: one of the fish wasn’t growing properly. 

We conducted a thorough investigation and tried various methods before finally identifying the root cause. This journey is what inspired me to write this piece.

So, why do Angelfish sometimes fail to grow as expected? What are the signs that their growth is being hindered? And what’s the normal size for an Angelfish?

I’m going to address all these questions in this article. Let’s get started.

What’s the Ideal Growth Rate for Angelfish?

The ideal growth rate for angelfish varies, but generally, healthy juveniles should grow about a quarter inch per month.

In the first six months, rapid growth is expected, and by the end of one year, they can reach about 50-60% of their adult size.

Factors like genetics, diet, and tank conditions significantly influence their growth rate.

Signs Your Angelfish Isn’t Growing Correctly

Signs of incorrect growth in angelfish include stunted growth, where the fish remains noticeably smaller than its peers of the same age.

Other signs are a thin or emaciated appearance and lack of vitality or activity.

Why Isn’t My Angelfish Growing?

There could be a few reasons why your angelfish isn’t growing as expected. Let’s take a look at what you should think about:

1. Inadequate Nutrition

Angelfish require a balanced diet rich in nutrients to grow properly. A diet lacking in essential vitamins, minerals, and proteins can lead to stunted growth.

  • Insufficient Proteins: Angelfish, especially juveniles, need high protein content in their diet for optimal growth. A diet with less than 30-40% protein can significantly hinder their development.
  • Lack of Variety: A monotonous diet can lead to nutritional deficiencies. Angelfish thrive on a varied diet including flakes, live foods, and vegetables.
  • Identification Tip: Besides stunted growth, look for signs like faded colors or a lack of appetite, which can indicate nutritional deficiencies.

Also Read: Why Is My Angelfish Not Eating?

2. Poor Water Quality

Water quality is crucial for the health and growth of angelfish. High levels of nitrates, ammonia, or incorrect pH can adversely affect their growth.

  • Toxic Substance Accumulation: Ammonia and nitrite levels above 0 ppm and nitrate levels above 20 ppm can stress angelfish, impeding their growth.
  • Unsuitable pH Levels: Angelfish prefer a pH range of 6.8 to 7.8. Fluctuations outside this range can cause stress and hinder growth.
  • Identification Tip: Look for signs like listlessness, frequent gasping at the surface, or clamped fins, which can indicate poor water quality.

3. Overcrowding

Overcrowding in an aquarium can lead to competition for food and space, impacting the growth of angelfish.

  • Stress from Competition: In overcrowded conditions, weaker angelfish may not compete well for food, leading to inadequate nutrition and stunted growth.
  • Reduced Water Quality: More fish in a tank can lead to rapid deterioration of water quality, affecting the health and growth of angelfish.
  • Identification Tip: Observe if the fish are constantly competing for space or hiding more than usual, as these behaviors can be indicators of overcrowding.

Also Read: Stress In Angelfish

4. Genetics

Genetic factors play a significant role in the growth and development of angelfish. Inherited traits can determine their potential size and growth rate.

  • Inherited Growth Limits: Some angelfish may have genetic predispositions that limit their maximum size, making them naturally smaller than others.
  • Genetic Disorders: Genetic abnormalities can also lead to stunted growth or deformities, impacting overall health and development.
  • Identification Tip: If your angelfish’s siblings or parents were also small or had growth issues, it could indicate a genetic factor at play.

5. Disease or Parasitic Infection

Diseases and parasitic infections can severely affect the health and growth of angelfish. These ailments can lead to stunted growth if not promptly addressed.

  • Nutrient Absorption Interference: Parasites like worms can interfere with the absorption of nutrients, depriving the fish of essential growth components.
  • Energy Diversion: Diseases can cause the fish’s body to divert energy from growth to fighting the illness, leading to stunted development.
  • Identification Tip: Look for symptoms like abnormal swimming, bloating, white spots, or lethargy, which can signal disease or parasitic infection.

Treating an Angelfish That’s Not Growing

If your angelfish has suddenly halted its growth, just follow these steps:

1. Nutritional Adjustment

Proper nutrition is key to resolving growth issues in angelfish. A well-balanced diet promotes healthy development and can reverse stunted growth.

  • Increase Protein Intake: Feed a diet comprising at least 40-50% protein. For instance, use high-quality pellet food with a protein content of 45% as the staple diet. It is worth considering these TetraCichlid Cichlid Flakes (link to Amazon).
  • Incorporate Variety: Supplement their diet twice a week with live or frozen foods like brine shrimp or bloodworms, providing essential nutrients not found in dry foods.
  • Supplement Vitamins and Minerals: Add a vitamin supplement to their food once a week. Look for supplements specifically designed for tropical fish. My recommendation: Seachem Nourish (link to Amazon).
  • Feeding Frequency: For juvenile angelfish, feed small portions 3-4 times a day, ensuring they’re consuming food within a few minutes to prevent overfeeding.

Also Read: How To Feed Angelfish

2. Water Quality Improvement

Good water quality is essential for the health and growth of angelfish. Maintaining an ideal aquatic environment can significantly impact their development.

  • Regular Water Changes: Perform 25% water changes weekly. Use a gravel vacuum to remove waste from the substrate, keeping the tank clean.
  • Monitor Water Parameters: Test water parameters weekly using a reliable aquarium test kit. Aim for ammonia and nitrites at 0 ppm, nitrates below 20 ppm, and a pH of 6.8 to 7.8. I personally use this API Freshwater Master Test Kit (link to Amazon).
  • Adequate Filtration: Use a filter rated for at least 1.5 times your tank’s volume. For a 50-gallon tank, use a filter rated for 75 gallons to ensure efficient filtration.
  • Temperature Consistency: Maintain a consistent temperature between 76°F to 80°F. Use an aquarium heater with a thermostat to regulate the temperature.

Also Read: Angelfish Water Parameters

3. Population Management

Managing the population in your aquarium can prevent overcrowding, which is crucial for the growth and health of angelfish.

  • Appropriate Tank Size: Ensure your tank is large enough for the number of fish. As a general rule, provide at least 10 gallons of water per angelfish.
  • Regular Monitoring of Fish Population: Keep a close eye on the number of fish in the tank. If breeding occurs, be prepared to relocate some fish to prevent overcrowding.
  • Provide Adequate Space: Arrange the tank with enough hiding spots and open swimming areas. Use plants and decorations to create a spacious environment.
  • Avoid Aggressive Tank Mates: Select tank mates carefully. Avoid fish that are overly aggressive or significantly larger, as they can stress angelfish and hinder their growth.

4. Selective Breeding Practices

Implementing selective breeding practices can improve the genetics and overall health of future angelfish generations, aiding in their growth and development.

  • Choose Healthy Breeders: Select breeding pairs that are robust, active, and have shown good growth patterns, as these traits can be passed on to their offspring.
  • Observe Genetic Traits: Pay attention to the size and growth rate of the parent fish. Avoid breeding angelfish that have shown stunted growth or other genetic issues.
  • Quarantine New Fish: When introducing new breeders, quarantine them first to ensure they’re healthy and won’t introduce undesirable traits or diseases into your breeding stock.
  • Record Keeping: Maintain records of breeding pairs and their offspring’s growth patterns to identify and strengthen desirable traits over successive generations.

Also Read: Angelfish Breeding Guide

5. Disease and Parasite Treatment

Treating diseases and parasites promptly is crucial for the health and growth of angelfish. Effective treatment can restore their well-being and encourage normal growth.

  • Regular Health Checks: Inspect your angelfish regularly for signs of illness or parasites, such as white spots, lethargy, or abnormal swimming.
  • Use of Medications: If a disease or parasite is identified, use the appropriate medication as prescribed. You can treat a wide spectrum of conditions with the Seachem PolyGuard (link to Amazon).
  • Isolate Affected Fish: Quarantine sick fish to prevent the spread of disease and allow for targeted treatment. This also reduces stress on the healthy fish.
  • Maintain Water Quality During Treatment: Ensure optimal water conditions during treatment. Some medications can affect water quality, so extra monitoring and adjustments may be necessary.

Also Read: Angelfish Diseases

How Large Should My Angelfish Be?

Adult angelfish typically reach a size of about 6 inches in length and up to 10 inches in height, including the fins.

The size can vary depending on the specific breed and tank conditions. It’s important to remember that full growth can take up to two years, so patience is key.

How Do Tankmates Affect Angelfish Growth?

Tankmates can significantly affect angelfish growth through competition for food and stress. 

Aggressive or overly active tankmates can intimidate angelfish, leading to reduced feeding and stunted growth.

It’s crucial to choose peaceful and compatible tankmates to ensure a stress-free environment conducive to healthy growth.

For example, stick to peaceful and gentle species like:

  • Corydoras Catfish (Corydoras spp.)
  • Dwarf Gourami (Trichogaster lalius)
  • Mollies (Poecilia spp.)
  • Platies (Xiphophorus maculatus)
  • Neon Tetras (Paracheirodon innesi)
  • Rummy-nose Tetra (Hemigrammus rhodostomus)
  • Bristlenose Pleco (Ancistrus spp.)

On the other hand, avoid aggressive fish like:

  • Red-tailed Shark (Epalzeorhynchos bicolor)
  • Tiger Barb (Puntigrus tetrazona)
  • Betta Fish (Betta splendens)
  • African Cichlids (Cichlidae family)
  • Goldfish (Carassius auratus)
  • Jack Dempsey (Rocio octofasciata)
  • Common Pleco (Hypostomus plecostomus)

Also Read: Angelfish Tank Mates

How to Assess an Angelfish’s Health Beyond Size

Assessing an angelfish’s health involves looking beyond just its size.

Observing their behavior, physical appearance, and interaction with the environment provides key insights into their overall well-being.

  • Activity Level: A healthy angelfish should be active and swim gracefully around the tank. Lethargy or unusual swimming patterns, like constantly staying at the bottom, can be signs of health issues.
  • Fins and Body Condition: Check for any tears, fraying in the fins, or unusual spots on the body. Healthy fins should be intact, and the body should be free from lesions or discoloration.
  • Eating Habits: A good appetite is a sign of health. If an angelfish is refusing food or eating less than usual, it may indicate a problem.
  • Interaction with Tank Mates: Observe how your angelfish interacts with others. Frequent hiding or aggression can be a sign of stress or discomfort, impacting their health.

Also Read: Angelfish Turning Black


For quick readers, here’s a short summary:

  • Angelfish not growing normally can be due to factors like inadequate nutrition, poor water quality, overcrowding, genetics, or disease, all of which require specific interventions.
  • Identifying and addressing issues like insufficient protein in diet, toxic water conditions, and overcrowding in tanks is crucial for the healthy growth of angelfish.
  • Effective solutions include dietary adjustments with increased protein and variety, improving water quality, and managing tank population to promote angelfish growth.
  • Genetic factors and diseases can significantly impact angelfish growth; selective breeding and prompt disease treatment are key to managing these issues.
  • Regular monitoring of angelfish’s size, behavior, and environment is essential to ensure optimal growth and health, taking into consideration their ideal growth rate and adult size.