The red eye tetra (moenkhausia sanctaefilomenae) was once among the most popular and widely kept tetras in aquariums. A school of these characins can infuse any tank with vibrancy and movement. However, in recent years, their popularity has declined as other species have taken precedence in the aquarium hobby.
This fish is peaceful and active, making it an excellent choice for community tanks. It thrives best in groups, unlike its relative, the redeye tetra. Regardless of whether there are three, eight, or even twenty individuals in the tank, red eye tetras will always swim together as a cohesive school.
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Habitat in the wild
The red eye tetra belongs to the family Characidae, a large and diverse group of freshwater fish that includes many well-known aquarium species, such as tetras, piranhas, hatchetfish, and pencilfish. While most members of this family are native to South America, some species can also be found in different parts of the world.
First described in 1907, the red eye tetra is native to various river systems across Brazil, Argentina, and Paraguay. In their natural habitats, they prefer slow-moving, heavily vegetated waters, such as streams, rivers, and flooded areas filled with dense aquatic plants. They may also venture into tributaries in search of food among the thick vegetation.
As a schooling fish, red eye tetras thrive in groups, which not only provides safety from predators but also facilitates their natural feeding behavior. They primarily feed on insects and other small invertebrates, making them an important part of their ecosystem.
| Characteristic | Description |
|---|---|
| Scientific Name | Moenkhausia sanctaefilomenae |
| Common Name | Red Eye Tetra, Lamp eye tetra, Monk tetra |
| Family | Characidae |
| Origin | South America (Brazil, Argentina, Paraguay) |
| Adult Size | Approximately 2 to 2.5 inches (5 to 6 cm) |
| Lifespan | 3 to 5 years or longer with proper care |
| Behavior | Peaceful, shoaling fish; prefers to swim in schools |
| Tank Size | Minimum 20 gallons for a small group |
| Water Temperature | 72°F to 82°F (22°C to 28°C) |
| pH Range | 6.0 to 7.5 |
| Water Hardness | Soft to moderately hard (dGH 5 to 15) |
| Tank Region | Middle to top levels of the aquarium |
| Diet | Omnivorous; accepts flake, pellet, and live/frozen foods |
| Compatibility | Generally peaceful, suitable for community tanks |
| Tank Level | Middle to top levels of the aquarium |
| Water Flow | Prefer slow-moving water |
| Lighting | Moderate to low lighting levels |
| Breeding | Egg-scatterer; requires spawning mops or dense plants |
| Sex Differences | Males may have more intense coloration and smaller size |
Description
Size
The red eye tetra typically reaches an adult size of approximately 2 to 2.5 inches (5 to 6 centimeters) in length. This size is important for aquarists to consider when setting up a tank, as it affects stocking density and compatibility with other species.
Males and females are generally similar in size, although males may appear slightly smaller and more slender than females. While there can be some variation in size among individuals, the 2 to 2.5-inch range is typical for adult red eye tetras in the aquarium hobby.
Lifespan
On average, red eye tetras have a lifespan of about 3 to 5 years in a well-maintained aquarium. However, with excellent care and favorable conditions, they can live even longer, potentially reaching up to 5 to 7 years.
Body
The red eye tetra has a sleek and elongated body shape, characteristic of most tetra species. Its body is slightly compressed from the sides, giving it a streamlined appearance that aids in swimming agility and helps it evade predators in its natural habitat.
Two types of red eye tetras are commonly recognized by aquarists:
- Red Eye Tetra: This type features the typical elongated body and is known for its vibrant coloration and active swimming behavior. The striking red eye and iridescent scales make it a popular choice for community tanks. In the wild, these fish swim in schools, using their agility to navigate through dense vegetation and evade potential predators.
- Balloon Red Eye Tetra: This variant is smaller and has a body shape that is wider than long, resulting in a more rounded appearance. The balloon red eye tetra often appears bloated due to abnormal or excessive fluid retention in its body, which can be a genetic trait or related to environmental factors. This unique shape has made it popular among aquarists for its aesthetic appeal, but it may require special care considerations.
Understanding the differences in body shape between these two types is important for aquarists, as it can influence their care requirements and compatibility with other fish species in a community tank. For example, the rounded shape of the balloon red eye tetra may make it more susceptible to buoyancy problems or other health issues, so careful monitoring of water quality and diet is essential.
Additionally, the sleek body shape of the red eye tetra enables it to evade predators effectively, allowing for swift movements when swimming in schools. Maintaining a well-planted tank with plenty of swimming space will not only help these fish feel secure but also enhance their vibrant coloration. Proper lighting and a balanced diet can further amplify their natural beauty, making them a stunning addition to any aquarium.
Coloration
Its body is primarily silver or silvery-gold, adorned with a reflective sheen that beautifully catches and reflects light. This shimmering effect not only enhances its aesthetic value but also creates an engaging display in any aquarium setting.
The most distinctive feature of the red eye tetra is its bright red or orange-red eye, which stands out prominently against the silver body. This vibrant eye color serves as a key identification marker and adds to the overall charm of the fish. In well-maintained tanks with appropriate lighting, the colors of the red eye tetra can become even more pronounced, making them a focal point of the aquarium.
Additionally, the reflective qualities of their scales can create a mesmerizing effect as they swim in schools, further showcasing their active and social nature. This visual dynamic can significantly enhance the overall ambiance of a community tank, making the red eye tetra a popular choice among aquarists looking to add color and liveliness to their setups.
Difficulties in keeping
Caring for red eye tetras is relatively easy, making them an excellent choice for beginner aquarists. These fish are not particularly demanding, which allows newcomers to focus on fundamental aspects of aquarium maintenance without feeling overwhelmed.
As mentioned earlier, red eye tetras are active and peaceful, contributing to a lively aquarium atmosphere. Their social behavior is a standout characteristic; they thrive in groups and prefer to swim in schools of at least 5 to 6 individuals. Keeping them in larger schools not only enhances their comfort and reduces stress but also encourages natural behaviors, such as foraging and displaying social dynamics.
Care and keeping in a tank
Tank size
The tank size for red eye tetras is crucial and largely depends on the number of fish you plan to keep. These tetras are inherently social creatures that thrive in schools, making it essential to maintain groups of six or more to ensure their well-being and minimize stress.
For a small group of red eye tetras, approximately 6 to 8 individuals, a minimum tank size of 20 gallons (75 liters) is recommended. This size provides ample space for the fish to swim comfortably while also allowing room for plants and decorations that create a suitable environment. A well-planted tank mimics their natural habitat, promoting their active behavior and social interactions.
However, it is important to note that larger tanks are generally more beneficial for fish. They offer more stable water conditions, which can lead to better overall health and reduced stress levels. If you plan to keep a larger school of red eye tetras or wish to include other compatible fish species in the same aquarium, considering a larger tank—ideally 30 gallons (113 liters) or more—would be prudent. A larger tank not only accommodates additional fish but also enhances the filtration system’s efficiency, helping maintain a clean and healthy environment for all inhabitants.
Water parameters
These tropical fish thrive in a moderately warm environment and require specific conditions to flourish.
- Temperature: A range of 72°F to 82°F (22°C to 28°C) is ideal for red eye tetras. Consistent temperatures within this range promote optimal metabolic function and overall health.
- pH Level: Red eye tetras prefer slightly acidic to neutral water conditions, with a pH level between 6.0 and 7.5. Regular monitoring of the pH is essential to ensure stability, as sudden fluctuations can lead to stress or health issues.
- Water Hardness: They thrive in soft to moderately hard water, with a general hardness (GH) level between 5 and 15 degrees. This range mimics their natural habitat and supports their physiological needs.
- Ammonia and Nitrite: Both ammonia and nitrite are toxic to fish and should be maintained at 0 ppm. Proper tank cycling and regular water changes are vital to achieve these levels, ensuring a safe environment for your tetras.
- Nitrate: While nitrate is a less toxic byproduct of the nitrogen cycle, it is important to keep its levels below 20 ppm. Regular water changes and careful monitoring will help maintain safe nitrate levels.
- Filtration: A good filtration system is essential for maintaining water quality. It helps remove debris and harmful substances, ensuring a healthy environment for the fish. Choosing a filter that is appropriate for the tank size will aid in effective water circulation.
- Water Flow: Red eye tetras prefer slow-moving water, so it’s crucial to avoid strong currents that may cause stress. Creating areas of low flow with plants and decorations can provide refuge and promote comfort.
Decor
Creating a suitable and visually appealing aquarium decor for red eye tetras is essential for mimicking their natural habitat while providing them with areas to explore, hide, and feel secure. This enriched environment enhances their overall well-being and promotes natural behaviors.
Aquatic plants play a vital role in this setup, as red eye tetras thrive in habitats rich in vegetation. Incorporating live plants such as Amazon swords, Java ferns, and Anubias not only provides hiding spots for the fish but also contributes to improved water quality. Live plants absorb excess nutrients, which helps maintain a balanced ecosystem within the tank and produces oxygen, further supporting the health of the fish.
Adding driftwood and rocks creates additional hiding places and breaks up the swimming space, resulting in a more natural-looking environment. These features offer shelter for the tetras, allowing them to feel secure while also serving as anchor points for attaching plants. Additionally, driftwood can leach beneficial tannins into the water, which may positively affect the fish’s health and create a slightly acidic environment that is ideal for red eye tetras.
Incorporating floating plants, like water lettuce or frogbit, can help diffuse lighting and create shaded areas within the aquarium. This mimicry of their natural habitat, characterized by moderate to low lighting levels, reduces stress and encourages natural behaviors. Floating plants not only create shaded areas but also help reduce algae growth by blocking excessive light from reaching the substrate.
Choosing a sandy or fine-grained substrate replicates the riverbed or stream bottom where red eye tetras are commonly found. A natural-colored substrate enhances the overall aesthetic of the aquarium while promoting a more authentic environment, allowing the fish to exhibit natural foraging behaviors.
By thoughtfully selecting and arranging these elements, aquarists can create a captivating and functional environment that supports the health and happiness of red eye tetras. Moreover, utilizing aquascaping techniques, such as creating layers with taller plants in the back and shorter ones in the front, can enhance the visual appeal and make the aquarium more inviting for both the fish and viewers. Regular trimming of live plants and cleaning of decorations is essential to keep the tank looking attractive and to prevent overcrowding, ensuring that all elements remain beneficial to the red eye tetras environment.
Tank mates
The red eye tetra is an excellent addition to community tanks, provided they are kept in schools, as these social fish thrive in groups. However, due to their active nature, they can inadvertently intimidate calmer fish. Therefore, it’s essential to select compatible tank mates that exhibit similar activity levels. Suitable companions include the black skirt tetra, emperor tetra, and cardinal tetra, all of which can match the red eye tetra’s lively demeanor.
It’s important to note that red eye tetras may exhibit fin-nipping behavior, particularly towards fish with long, flowing fins. As such, it’s advisable to avoid keeping them with slow-moving or long-finned species, such as angelfish, as this can lead to stress or injury.
If suitable tank mates are limited, you can mitigate this fin-nipping behavior by maintaining a larger school of red eye tetras. In a larger group, a natural hierarchy often develops, allowing the fish to focus on their own species and reducing their tendency to nip at the fins of other fish.
Diet
Red eye tetras are omnivorous fish with a versatile diet, thriving on a variety of foods in their natural habitat, including small insects, zooplankton, algae, and plant matter. To ensure their health and vitality in an aquarium setting, it’s crucial to provide a balanced diet that mimics their natural feeding habits.
A staple diet for red eye tetras can consist of high-quality flake or pellet food specifically formulated for tropical fish. When selecting these products, look for options that contain a diverse range of nutrients suitable for small community fish, as this will serve as their primary food source.
In addition to staple foods, red eye tetras enjoy live and frozen options such as brine shrimp, bloodworms, daphnia, and mosquito larvae. These types of foods closely resemble their natural diet and are rich in essential proteins and nutrients, which contribute to their overall well-being.
Feeding should be done in small portions multiple times a day rather than providing one large meal. This approach mimics their natural foraging behavior, ensuring they have continuous access to food throughout the day. It also helps promote their activity levels and reduces competition among tank mates.
It is essential to avoid overfeeding, as excess food can lead to water quality issues and negatively impact the health of the fish. Regularly monitoring your fish’s behavior and adjusting their diet as necessary will help keep them healthy and thriving in your aquarium. By providing a varied and balanced diet, you can ensure that your red eye tetras remain vibrant and active, enhancing the overall dynamics of your community tank.
Gender differences: male vs female
In red eye tetras, it can be challenging to distinguish between males and females based solely on external characteristics, especially when they are not in breeding condition. The differences between the sexes are generally subtle and become more pronounced during the breeding season.
One guideline for identifying male and female red eye tetras is their size. Females are often slightly larger and more robust than males, though this difference may not always be significant.
Coloration is another distinguishing factor, especially during the breeding season. Males tend to exhibit more intense coloration, particularly around their fins and body, appearing brighter and more vibrant than females.
Body shape also plays a role in differentiation. Males may have a slightly more streamlined and elongated body compared to females, who often appear plumper, especially when carrying eggs.
Fins can provide another clue, as males might have slightly more extended or pronounced dorsal and anal fins. However, this distinction can be subtle and not always reliable for identification.
Behavior is perhaps the most telling sign during the breeding season, as males often display more active and assertive behavior, especially when courting females. Observing these behaviors can provide insight into which fish are male and which are female.
It’s important to note that these differences can be difficult to spot in young or non-breeding red eye tetras. If you’re interested in establishing a male-female pair for breeding purposes, the best approach is to observe their behavior during the breeding season. This is when the distinctions become more apparent, allowing for more accurate identification.
Breeding
Red eye tetras typically reach reproductive maturity at around 10 months of age. For successful breeding, it’s essential to set up a separate spawning tank with a minimum capacity of 2 gallons. This tank should be covered to prevent jumping and provide a secure environment for the fish.
To create an optimal breeding environment, the spawning tank should contain Java moss or a separating grid on the bottom. The water conditions are critical: it should be warmer, ideally between 24-28 °C, slightly acidic with a pH of 6.0 to 6.8, and soft, with a hardness level below 6 degrees. Preparing the fish for spawning involves placing them in separate tanks where they can be well-fed and have a diet enhanced with plant-based foods for at least a few days before introducing them to the spawning tank.
Once the fish are moved to the spawning tank in the evening, they will typically engage in a mating display among the plants the following morning. The female can lay up to 1,000 sticky eggs, which may adhere to the bottom of the tank or cling to the leaves of the plants.
After the spawning period, it’s essential to remove the adult fish from the tank to prevent them from eating the eggs. Following their removal, light aeration should be introduced to the tank. The eggs are quite fruitful and typically take about 1 to 2 days to incubate. By the 5th or 6th day, the larvae transform into juveniles and begin to feed on small nauplii of brine shrimp.
Since the juveniles are tiny at birth, it’s crucial to provide appropriately sized food, such as small brine shrimp nauplii, cyclops nauplii, rotifers, or infusoria. Despite a well-balanced and nutritious diet, juvenile red eye tetras grow slowly. Therefore, it’s important to maintain consistent feeding and water quality to support their development into healthy adults. By ensuring the right conditions and diet, aquarists can successfully raise red eye tetra fry to maturity.