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The red eye tetra is not one of the most well-known Tetra species. However, it’s by far one of the most peaceful and even-tempered. For beginners and experienced fishkeepers alike, this fish can be a sophisticated addition to any aquarium.

This species has striking colors, and is great for tanks with darker backgrounds that illuminate these colors. On top of this, Red Eye tetras are easy and adaptable. They thrive best in groups of six or more, in well-planted, dim aquariums, which will give them a calm and comfortable environment to thrive in.

Though they may seem simple, and easygoing, the Red Eye Tetra can be an exceptional beauty if properly understood. Read on for the best food, suitable red eye tetra tankmates, and general care tips for this unusual species.

Breed Overview

Red Eye Tetra Species Summary

The Red Eye Tetra falls under the scientific name (Moenkhausia sanctaefilomenae), Is a very popular species of Schooling Tetra fish that is native to mostly the São Francisco, Paraná, Paraguay, and Uruguay river basins in Central South America. It is quite a popular aquarium fish, especially in Asia and Eastern Europe.

You may wonder if this unique fish has any closely living relatives.

The Red Eye Tetra mainly forms part of a group that also contains two other species (Moenkhausia forestii) that are mainly found in upper Paraguay and upper Paraná, and the (Moenkhausia oligolepis) well known in the Amazon, Paraguay, and Guianas river basins.

What Does A Red Eye Tetra Look Like?

The red eye tetra generally has a bright, shiny silver body. It has a black basal half of the tail that has white edging and red eyes with a bright orange or yellow circle around the eye. What’s more, red eye tetra size is slightly larger than some other tetra species, closer to that of a molly or platy fish.

Beyond this, it has black fins, and sometimes vertical bars on the sides of the body. Red-eye Tetras are a medium-sized Tetra species and ideal for larger communal Aquariums as they are peaceful shoaling fish.

Variation Within Red Eye Tetra Size and Appearance:

• Males and Females – There are not many differences between male and female Red Eye Tetras, especially when they are young. Adult females exhibit a rounder abdomen and are usually larger than males. Males tend to be slimmer and more streamlined, with a pointed dorsal fin. Females will fill up with eggs and have a very rounded belly, while males become quite colorful when they are ready to mate with a female.
• Variations – Though many different Tetra species in all shapes, sizes, and colors do exist, the Red Eye Tetra does not have many color variations. There is however what is known as the Balloon Red Eye Tetra, a quirky and comical-shaped Tetra with similar coloring. This has a much more rounded shape, resembling a Balloon.  Another Red Eye Tetra species (Arnoldichthys spilopterus) African Red-eyed Tetra, exists and is found mainly in Nigeria in Africa. The African Red Eye Tetra has a more translucent silvery body with a light yellow vertical line across the body. With a yellow half-ring over the top part of the eye, it is actually a separate species! However, it can be easy to confuse the two, as it also has a black marking on the dorsal fin and yellow at the base, with a translucent caudal fin, or tail.

Lifespan And Red Eye Tetra Size

The Red Eye tetra has an average adult size of 7 cm (2.8 in), in males, with females slightly larger and rounder. A life span of around 5 years can be expected with proper care and nutrition.

Temperament Of The Red Eye Tetra

For the most part, they are a more peaceful Tetra species. The red eye tetra enjoys shoaling in groups of at least six or more of their species. They prefer using open spaces for swimming in the center of the aquarium and are generally easygoing. Single Red Eye Tetras can be aggressive and nippy, however.

There have also been reports from owners where Red Eye Tetras have taken a nip at the fins of other slow-moving, long-finned fish.

Most Tetra species are very peaceful when kept in groups. They are social and mostly keep to themselves, though there are a few more aggressive Tetra species.

Which ones are these?

Steer clear of the following species as red eye tetra tankmates and your tank should be fine:

• Bucktooth Tetras (Exodon paradoxus)
• Vampire Tetra Fish (Hydrolycus scomberoides)
• Lemon Tetras (Hyphessobrycon pulchripinnis)
• Black Skirt Tetras (Gymnocorymbus ternetzi)
• Congo Tetras (Phenacogrammus interruptus)
• Serpae Tetras (Hyphessobrycon eques)
• Panda Tetras (Aphyocharax paraguayensis)

Care Requirements

Ideally, Red Eye Tetras are surprisingly resilient. They are adaptable to most living conditions and are perfect for both newer and experienced aquarists. To keep them happy and healthy it is always best to stick to their preferred care needs. This also means creating an environment similar to their natural one.

Water Parameters and Aquarium

To start it is vital to create a proper and comfortable aquarium that is suitable for the red eye tetra. They need to be kept in a group of six so the tank cannot be smaller than 20 gallons,  and 30 gallons is the best option. Keep in mind for communal aquariums, or should you want to add fish of other species, you will need more space.

• Water Conditions – Red Eye Tetras are freshwater fish that prefer slightly more tropical climates with temperatures of around 22–28°C (71.6–82°F), a pH range between 6.0 and 8.0, and clean moderately hard water conditions. Even though they are adaptable to most water conditions, these preferences have proven to be ideal for red eye tetras.
• Filtration – Tetras in general do not produce much waste, depending on the size of the school, and other tank companions. Because Red Eye Tetras are not the strongest swimmers it is vital to have a functional filter that has a very slow current. Typically, Canister, Hang Back, or even air-powered sponge filters are ideal. Proper aeration and high oxygen levels are essential for the red eye tetra, and an additional sponge filter or natural plants can come in handy.
• Heater – Red Eye Tetras thrive in slightly warmer, more tropical temperatures. Therefore you will need a heater and proper thermometer to provide them with the correct water temperatures. Inline or submersible heaters with a built-in thermometer are ideal.
• Light – In their natural environment Red Eye tetras are prevalent in areas that have dense forestry with dim and filtered light. In their aquarium, they will enjoy some filtered light, or dim light, provided using floating plants, and dense rooted plants. Red Eye tetras are well known to have an aversion to bright light.

Tank Decor

Decorating your tetra aquarium is where the fun starts, as it can be very creative. However, it is always advisable to rather opt for a more natural-style aquarium in which they can feel safe and at home.

Keep in mind that in their natural environment, the red eye tetra is used to slow-moving rivers, with lots of vegetation and hiding spaces. This also includes plenty of shade from above. The bottoms of these rivers are usually covered with leaves and detritus, with fine river sand and rocks.

• Substrate – Though Red Eye Tetras are mostly middle-dwelling fish, the substrate in your aquarium can create a more alluring appeal, and provide foraging grounds for additional bottom-feeding fish. Darker-colored substrates are usually favored as they intensify the colors of each red eye tetras. Fine-grained sandal, or very fine gravel, is usually the best and most natural substrate.
• Ornaments – Tetras in general need some open space for swimming, though they similarly enjoy a few hiding spots. Natural décor such as Rocks, driftwood, and caves can create a safe and suitable environment. Likewise, you have the choice of synthetic plants such as silk and fabric plants, or live plants.

Live Plants

Live plants have quite a few benefits for any aquarium. They can help to provide shade, oxygenate the water, and also have water-cleaning abilities. Live plants in some cases also provide a tasty snack for your Tetras. The fallen leaves and detritus from live plants will recreate their natural surface habitat, and provide food for bottom-dwelling fish. With that said, here are a few good choices in live plants for Red Eye Tetras:

• • Java Fern – Java ferns have longer larger leaves as hiding spots, and most tetras will not try to eat them.
  • Java Moss – A favorite in tetra tanks as it grows easily and is remarkably resilient.
  • Anubias – Ideal for smaller tanks, and hardy plants perfect for Tetra aquarium conditions.
  • Christmas Moss – Attractive and ideal for hiding spots, Christmas moss can float or be kept on the surface of rocks and décor.
  • Pennywort – Pennywort is a tall rooted plant or it can be kept floating.
  • Frogbit – A floating plant though it will need ample light to thrive.
  • Amazon Sword – One of the hardiest plants that grows tall, and has broad flat leaves.
  • Hornwort – Ideal as a background plant that grows tall and requires little light.
  • Anacharis – A similarly hardy and ideal plant
  • Cryptocoryne Wendtii – A rooted plant found in many different color variations.

Lastly, and very crucial, Tetras are notorious for jumping out of their tanks. This is why keeping a lid on the tank is always safer.

Feeding Your Tetras

Tetras are naturally omnivores and enjoy anything from worms, insects, small crustaceans, and even plant matter in their natural habitat. Thus, the red eye tetra should be fed a varied diet consisting of both plants and proteins.

Do you want more than just plain fish food for your fish? There are a number of other options you can use to supplement their diet.

What To Feed

• Pellets and Flakes – As a staple tetras require a quality pellet or flake food that offers balanced nutrition.
• Live and Frozen Foods – Live or freeze-dried meat-based foods such as Bloodworms, Brine Shrimp, Daphnia, and Insect Larvae can be fed occasionally.
• Plant Material –Vegetables including Greens, Carrots, Lettuce, and Cucumbers that are thinly sliced and blanched are essential.

How To Feed

The Red Eye Tetra will eat with enthusiasm, though not much. Give them enough to eat twice a day, for them to finish within a couple of minutes to reduce excess waste in the tank.

Introducing Your New Fish

After the aquarium is ready, fully cycled and you have everything you need, it is time for the big moment.

Did you know you can’t just introduce a fish to a new aquarium and expect them to thrive?

There are right and wrong ways to introduce your Red Eye Tetras to their new home. In the case of an established communal aquarium, ensure that all the fish have been fed and that the lights are dimmed.

Choosing Healthy Red Eye Tetra Fish

Take care when purchasing new fish that you source them from a trusted breeder or pet store. Obtaining a healthy group of juvenile fish will ensure that they live up to their full potential.

Ensure that none of the fish have a bloated belly, any white spots, or unnatural markings on their fins and body. Their eyes need to be clear and bright, and the fish must be active and lively swimming around, rather than cowering in a corner.

Placing A Fish In The Tank

There is a relatively standard procedure to place any new fish into an aquarium which involves the following steps:

1. First, allow your tetras to float on the surface of the tank in their original bag for around 20 minutes to get them used to the water temperatures.
2. Remove a cup of the water from the bag and replace it with water from the tank.
3. Repeat the second step until you have removed and replaced most of the water in the bag, allowing for intervals of at least 15 minutes per water change.
4. Slowly release the new tetras into the tank, avoiding allowing too much of the dirty water from the bag to enter the tank, as it will contain much waste from the acclimating period.

Suitable Red Eye Tetra Tank Mates

You may already have an established tank with a few other fish species or would like to choose some more species to add to the aquarium, However, you must take care with this endeavor as not all fish species get along very well.

Two key factors to keep in mind are:

1. The temperament and behavior of each species.
2. The water requirements of the species.

Many Red Eye Tetra owners have found bettas and Red Eye Tetras are the worst tank mates. However, if you’re looking for some more suitable red eye tetra tankmates, the following species tend to get along:

• Bottom feeders such as Corydoras, Kuhli Loaches, Horsehead Loaches, and Pygmy Corydoras.
• Most Rasbora Species.
• Most Danios.
• Barbs except Tiger Barbs.
• Dwarf, Pearl, and Honey Gouramis
• Bolivian Ram Cichlids
• Other peaceful Tetra species such as Neon and Cardinal Tetras.
• Nerite Snails are similarly an excellent choice, as they do not reproduce as fast or create much waste.

Tank Maintenance And Tank Equipment

The Red Eye Tetra will thrive in pristine clean water, making regular maintenance a necessity:

1. A weekly water change of at least 255 of the water in the tank is required, following these steps:
2. Use a siphoning hose to remove 25% of the tank water from the bottom of the aquarium.
3. Prepare the same amount of water using clean conditioned water that is similar in temperature.
4. Gradually add the new water to your tank.
5. Clean any ornaments or synthetic plants covered in algae, and ensure that you clean the filter as necessary.

Health Issues In Tetras

Red Eye Tetras are relatively sensitive to common freshwater fish health conditions.

The main culprits causing these conditions include:

• Poor Water Conditions – Water that is not clean, with high levels of ammonia, causes stress and physical damage to fish that may lead to conditions such as Fin Rot, and Infections.
• New Fish or Plants – Parasites or worms can easily transfer from new fish or plants that you add to the communal aquarium. This will then affect the rest of your fish. Therefore, it is always vital to quarantine and properly check any new plants and fish first.
• Improper Diet – Overfeeding, or feeding foods that are not suitable for Tetras can cause digestive upsets, and bloating, and excess food will cause waste that can spike ammonia levels.
• Physical Damage – Handling your fish can cause an injury or remove their protective slime coating. Similarly, any décor or plants in the aquarium that have sharp edges, or rough surfaces could cause harm. Then again more aggressive species may pick on slower and shy fish, causing physical damage. Physical damage may sometimes come from a bacterial infection, like fin rot, too.

The main Freshwater Fish issues are as follows:

1. Swim Bladder Disease – Also referred to as Dropsy. It occurs when there is a fungal or bacterial infection in the swim bladder of your fish. Your fish will struggle to stay upright and will float or lay sideways.
2. Fin Rot – Fin or Tail Rot is an infection as a result of physical damage to the fish. There may be a ragged appearance to the tail and fin with red streaks, or colored patches. Antibacterial medication is usually the best line of treatment.
3. Ich/White Spot Disease – Essentially a Protozoan parasite, the parasite thrives in poor water conditions, and is infectious. It causes small white spots on the skin of your fish. Treatment is easy and quarantine of your fish will be necessary for at least 7 days in pristine water conditions.

Breeding Red Eye Tetras

Red Eye Tetras are relatively easy to breed, As mentioned, mature females have a more rounded larger shape. They have round dorsal fins, whereas males are smaller with slim bodies and pointed dorsal fins.

You will need a separate breeding tank, as Tetras will consume their eggs and young fry. The breeding tank should have dense vegetation with softer and slightly more acidic water.

The mating pair will spawn, after which case you must remove them both from the breeding tank. The eggs will hatch a day or so after being laid and the young fry can be fed infusoria or baby brine shrimp after two to three days.

Final Thoughts

The Red Eye Tetra is one of the less popular Tetra species, though it is one of the more peaceful and hardy species from the Tetra family. As long as they are kept in groups, and you give them proper care, they are hardy and adaptable fish. In fact, the red eye tetra gets along with most other species that are relatively easy to keep. Thus, they are a great start for a peaceful community tank that will give you endless interest and entertainment.

Frequently Asked Questions