Red Eye Tetra: A Comprehensive Guide to Care, Behavior, and Breeding

Red Eye Tetra: A Comprehensive Guide to Care, Behavior, and Breeding

Table of Contents

Red Eye Tetra: A Comprehensive Guide to Care, Behavior, and Breeding

The Red Eye Tetra (Moenkhausia sanctaefilomenae) is a captivating freshwater fish species that has become increasingly popular among aquarium enthusiasts. Known for its striking red eyes and vibrant coloration, the Red Eye Tetra is a visually appealing addition to any aquarium. In this guide, we will delve into all aspects of caring for and understanding these unique fish.

AppearanceSlender body, red/orange eyes, silver body color
Average Size1.5 to 2 inches (3.8 to 5.1 cm)
Lifespan3 to 5 years
Male vs. FemaleSimilar external characteristics; females may appear slightly rounder during breeding
PregnancyEgg layers, fertilization occurs externally during spawning
Tank SizeMinimum 20 gallons for a small school of Red Eye Tetras
Water ParametersTemperature: 72-78°F (22-26°C), pH: 6.0-7.5, Water Hardness (GH): 4-12 dGH
Tank SetupFine gravel or sand substrate, live/silk plants, driftwood, rocks for hiding
Common DiseasesIch (White Spot Disease), Fin Rot, Fungus
DietHigh-quality flakes, live/frozen foods (brine shrimp, daphnia, bloodworms), vegetables
Behavior & TemperamentPeaceful, schooling fish best kept in groups
Tank MatesTetras (Neon, Cardinal, Ember), Corydoras Catfish, Small Rasboras, Dwarf Gouramis
Eggs laid on broad leaves or substrate, temperature increase to 78-80°F (25-27°C) to trigger breeding
source: wikipedia
Red Eye Tetra: A Comprehensive Guide to Care, Behavior, and Breeding


The Red Eye Tetra is named for its distinctive feature – its bright red eyes. This striking characteristic is complemented by a slender, elongated body that is translucent silver in color. Their fins are typically adorned with a vibrant red or orange hue, adding to their overall beauty.

Average Red Eye Tetra Size: Red Eye Tetras are relatively small fish, with an average size of 1.5 to 2 inches (3.8 to 5.1 cm) in length.

Red Eye Tetra Lifespan

Red Eye Tetras have a moderate lifespan when provided with proper care. On average, they can live for about 3 to 5 years in a well-maintained aquarium environment.

Red Eye Tetra Male vs. Female

Distinguishing between male and female Red Eye Tetras can be challenging, as they share similar external characteristics. However, during the breeding season, females may appear slightly rounder and plumper due to the presence of eggs.

Red Eye Tetra Pregnant

Red Eye Tetras are egg layers, which means they do not become pregnant in the traditional sense. Instead, females will lay eggs, and males will fertilize them externally during the spawning process. To encourage breeding, provide them with a suitable environment and conditions (covered in the “Red Eye Tetra Breeding” section).

When a female Red Eye Tetra is carrying eggs, her abdomen may appear slightly rounder and more swollen than usual. This is a sign that she is ready to spawn. However, the change in abdominal fullness is not as pronounced as in livebearing fish.


Proper care is essential to ensure the health and well-being of Red Eye Tetras in your aquarium. Let’s explore the key aspects of their care.

Red Eye Tetra Tank Size

When selecting a tank for your Red Eye Tetras, it’s essential to provide them with enough space to swim and thrive. A tank with a minimum capacity of 20 gallons is recommended, as this will allow for a small school of these fish to coexist comfortably.

Water Parameters

Maintaining the right water parameters is crucial for the overall health of Red Eye Tetras. Here are the ideal conditions:

ParameterIdeal Range
Temperature72-78°F (22-26°C)
pH Level6.0-7.5
Water Hardness (GH)4-12 dGH
Ammonia/Nitrite/Nitrate LevelsLow to None

Regular water testing and maintenance are essential to keep these parameters within the recommended ranges.

What to Put in Their Tank

Creating a suitable environment for Red Eye Tetras involves more than just water quality. It’s important to consider the following:

  1. Substrate: Use fine gravel or sand as the substrate, as Red Eye Tetras like to forage in the substrate for food.
  2. Plants: Live or silk plants will provide hiding spots and mimic their natural habitat. Red Eye Tetras appreciate densely planted areas.
  3. Decorations: Include driftwood and rocks to create caves and hiding places. This will help reduce stress and aggression among the fish.

Certainly, let’s delve into more detail about common diseases that can affect Red Eye Tetras and how to prevent and treat them:

Common Diseases of Red Eye Tetras

Maintaining the health of your Red Eye Tetras is paramount to their well-being. These fish, like any other, can be susceptible to various diseases. Recognizing the signs of illness early and taking appropriate action is crucial to ensuring their longevity. Here are some common diseases that Red Eye Tetras may encounter:

1. Ich (White Spot Disease):


  • White cysts or spots on the skin, fins, and gills.
  • Increased scratching against objects or substrate.
  • Rapid gill movement and lethargy.

Ichthyophthirius multifiliis, commonly known as “Ich” or White Spot Disease, is a protozoan parasite. It often appears when fish are stressed or when water conditions deteriorate.

Prevention and Treatment:

  • Maintain stable water parameters, including temperature, pH, and water quality.
  • Quarantine new fish to prevent introducing the parasite to an established tank.
  • Increase water temperature to 82-86°F (28-30°C) for a few days to speed up the parasite’s life cycle.
  • Use aquarium salt or anti-parasitic medications as directed to treat infected fish.

2. Fin Rot:


  • Deterioration of the fins, which may appear frayed or ragged.
  • Discoloration or redness at the base of the fins.
  • Reduced activity and appetite.

Fin Rot is typically caused by bacterial infections, often due to poor water quality or injuries. Stress can also weaken the fish’s immune system, making it more susceptible to this disease.

Prevention and Treatment:

  • Maintain excellent water quality with regular water changes.
  • Avoid overcrowding and provide suitable tank conditions.
  • Isolate infected fish to prevent the spread of the bacteria.
  • Administer antibiotics or antibacterial treatments as prescribed by a veterinarian or as per the manufacturer’s instructions.

3. Fungus:


  • Cotton-like or fuzzy growth on the skin, fins, or mouth.
  • Rapid deterioration of affected areas.
  • Decreased activity and appetite.

Fungal infections typically occur when fish have open wounds or injuries, often as a secondary infection following another illness or injury.

Prevention and Treatment:

  • Maintain clean water and excellent overall tank hygiene.
  • Address any injuries promptly to prevent fungal infections.
  • Isolate infected fish and treat with antifungal medications.

4. Parasitic Infections:

Various external and internal parasites can affect Red Eye Tetras. Symptoms may include visible parasites, erratic swimming behavior, weight loss, and reduced activity. Prevention includes maintaining optimal tank conditions and quarantining new arrivals. Consult with a veterinarian or experienced aquarist for proper diagnosis and treatment.

5. Stress-Related Diseases:

Stress weakens a fish’s immune system and can lead to various health issues. Minimize stress by providing appropriate tank mates, maintaining stable water parameters, and avoiding sudden changes in the aquarium environment.

6. Malnutrition:

Inadequate or imbalanced diet can lead to nutritional deficiencies. Ensure your Red Eye Tetras receive a varied and balanced diet to prevent this issue.

7. Bacterial and Viral Infections:

Less common but still possible, bacterial and viral infections can affect Red Eye Tetras. Symptoms may include ulcers, swelling, or unusual behavior. Consultation with an aquatic veterinarian may be necessary for proper diagnosis and treatment.

Important Note: When diagnosing and treating diseases in your aquarium, it’s essential to seek advice from experienced aquarists or veterinarians who specialize in fish health. Avoid using medications indiscriminately, as they can harm beneficial bacteria and other tank inhabitants.

Maintaining a clean and stable fish tank environment, providing a balanced diet, and closely monitoring your Red Eye Tetras for any signs of illness are essential practices to keep these beautiful fish healthy and thriving in your aquarium. Regular observation and proactive care will go a long way in preventing and managing common diseases.

Red Eye Tetra Food & Diet

Feeding Red Eye Tetras a balanced diet is crucial for their health and coloration. They are omnivorous and will accept a variety of foods, including:

  1. High-Quality Flakes: A staple diet for Red Eye Tetras can consist of high-quality flake food specially formulated for tropical fish.
  2. Live and Frozen Foods: Supplement their diet with live or frozen foods such as brine shrimp, daphnia, and bloodworms. These provide essential nutrients and variety.
  3. Vegetables: Offer blanched vegetables like spinach and zucchini to provide fiber and essential vitamins.

Remember to feed them in small, frequent portions to prevent overeating and maintain water quality.

Red Eye Tetra Behavior & Temperament

Red Eye Tetras are known for their peaceful nature, making them suitable for community aquariums. They are schooling fish, so it’s best to keep them in groups of at least six to eight individuals. In larger groups, they will exhibit their natural schooling behavior, which is both fascinating to watch and calming for the fish.

Red Eye Tetra Tank Mates

Selecting compatible tank mates is crucial for the well-being of your Red Eye Tetras. Ideal tank mates include other peaceful community fish such as:

  • Tetras: Neon Tetras, Cardinal Tetras, and Ember Tetras are excellent choices.
  • Corydoras Catfish: These bottom-dwelling fish are peaceful and won’t compete for space.
  • Small Rasboras: Harlequin Rasboras and Chili Rasboras are good options.
  • Dwarf Gouramis: These colorful fish can coexist peacefully.

Avoid keeping them with aggressive or larger species that may intimidate or prey on Red Eye Tetras.

Certainly, let’s delve into more detail on breeding Red Eye Tetras:

Red Eye Tetra Breeding

Breeding Red Eye Tetras can be a fascinating and rewarding experience for aquarium enthusiasts. These fish are relatively easy to breed when provided with the right conditions and environment. Here’s a step-by-step guide on how to encourage and facilitate their breeding:

1. Select a Breeding Pair:

  • Start by identifying potential breeding pairs from your group of Red Eye Tetras. Look for mature and healthy individuals.
  • Ideally, keep a higher ratio of females to males in the tank to prevent excessive aggression toward a single female during the breeding process.

2. Condition the Breeding Pair:

  • Prior to breeding, it’s essential to condition the breeding pair by providing them with a nutritious diet. Offer a varied diet that includes live and frozen foods to ensure they are in optimal breeding condition.

3. Create Breeding Conditions:

  • To trigger breeding behavior, gradually increase the temperature of the aquarium to around 78-80°F (25-27°C). This mimics the warmer waters of their natural habitat during the breeding season.
  • Ensure that the lighting in the tank is subdued. You can use floating plants to diffuse light and create shady areas.
  • Provide plenty of hiding spots in the form of plants, caves, or spawning mops. Red Eye Tetras will lay their adhesive eggs on the undersides of broad leaves, among fine-leaved plants, or on the substrate.

4. Observe Spawning Behavior:

  • As the conditions become favorable, the male Red Eye Tetras will begin to court the females by displaying vibrant colors and fin-flaring.
  • The female will lay small, adhesive eggs on the chosen surface, while the male will follow closely, fertilizing the eggs externally as they are laid.

5. Separate Eggs or Use a Breeding Tank:

  • If you want to maximize the survival rate of the fry, consider transferring the breeding pair to a separate breeding tank with similar water parameters. This prevents adult fish from consuming the eggs.
  • Alternatively, you can leave the eggs in the main tank, but be prepared for some of them to be consumed by other tank inhabitants.

6. Care for the Fry:

  • After a few days (typically 24-48 hours), the eggs will hatch into tiny fry.
  • Initially, the fry will rely on their yolk sacs for nutrition. Once the yolk sacs are absorbed, you can start feeding them with infusoria or commercially available liquid fry food.
  • Keep the water in the breeding tank pristine and maintain stable water parameters to ensure the best chance of fry survival.

7. Gradual Growth and Transition:

  • As the fry grow, you can gradually introduce finely crushed flakes or powdered fry food to their diet.
  • At about 4-6 weeks of age, the young Red Eye Tetras will be large enough to be transferred to a larger tank with their parents or to join the main aquarium community.

Breeding Red Eye Tetras can be a satisfying experience, but it may require some patience and attention to detail. Ensuring the right conditions, a proper diet, and a well-prepared breeding environment will increase your chances of successfully raising a new generation of these beautiful fish. Remember that not all breeding attempts will be successful, so be prepared for variations in outcomes.

Red Eye Tetra Eggs

When ready to spawn, Red Eye Tetras will lay their eggs on the underside of broad leaves or on the substrate. These eggs are adhesive and will stick to the chosen surface.

Red Eye Tetra Breeding Temperature

To trigger breeding behavior, gradually raise the temperature of the aquarium to around 78-80°F (25-27°C). Provide ample hiding spots and soft, slightly acidic water to replicate their natural breeding conditions.

In conclusion, Red Eye Tetras are captivating and easy-to-care-for freshwater fish that can thrive in a well-maintained aquarium. By understanding their unique characteristics, providing proper care, and creating a suitable environment, you can enjoy the beauty of these fish in your own home aquarium. Whether you’re a beginner or an experienced aquarist, the Red Eye Tetra is a fantastic addition to your aquatic collection.

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Lee Johnson

Lee Johnson

Aquarium Enthusiast

I love sharing my knowledge about all things aquarium related. I have been keeping aquariums for over 20 years and cannot imagine a life without an aquarium. 

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