Red Eye Tetra
Moenkhausia sanctaefilomenae
The Red Eye Tetra is a hardy, active schooling fish recognizable by the bright red upper half of its eye and a striking black and yellow band at the base of its tail. As a robust and highly adaptable species, it is excellent for beginners. However, they are highly active and can become 'fin nippers' if kept in groups smaller than 6 or in confined spaces.
Red Eye Tetra At a Glance
Red Eye Tetra Tank Requirements
Will Red Eye Tetra fit in your tank?
Care guides tell you what Red Eye Tetra needs, the next question is whether your tank can safely provide it. Test Red Eye Tetra against your tank size, maintenance needs, and the fish you already keep before you buy.
Red Eye Tetra Water Parameters
Red Eye Tetra Temperament & Compatibility
Red Eye Tetra Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard form of the Red Eye Tetra. Requires plenty of horizontal swimming space. May nibble on fine-leaved or soft aquatic plants.
Differs in 1 trait from base species
Also known as: Wild Type
Balloon Morph
A selectively bred 'short-body' or balloon morph. Because of their deformed spine and compressed internal organs, they are weaker swimmers and are prone to swim bladder issues. Requires lower flow than the standard form.
Differs in 3 traits from base species
Also known as: Balloon Red Eye, Short Body
Red Eye Tetra Care Guide Summary
The Red Eye Tetra, scientifically known as Moenkhausia sanctaefilomenae, belongs to the Characins family group. Adults reach a maximum size of approximately 7 cm and have a compressed body shape with a moderate growth rate. Classified as mostly peaceful, this species primarily occupies the mid-level and surface zones of the aquarium and produces a low level of biological waste.
To thrive, the Red Eye Tetra requires a freshwater only aquarium with a minimum volume of 75 litres and a tank length of at least 60 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 5.5–8.5 and a general hardness of 3–20 dGH. A moderate water flow is preferred.
The Red Eye Tetra is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Standard and Balloon Morph. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Red Eye Tetra Habitat Setup
When setting up an aquarium for the Red Eye Tetra, a moderate water flow best suits their natural preferences. Because this species occupies the mid-level and surface zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include dense planting to provide cover, break sightlines, and reduce stress. Keepers should note that live planted layouts may be difficult to maintain, as this species tends to uproot or consume vegetation.
Red Eye Tetra Compatibility Notes
Classified as mostly peaceful, the Red Eye Tetra is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, avoid housing with slow-moving or long-finned species that may become targets for fin nipping and their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the mid-level and surface zones can help reduce competition and territorial overlap.
Who Red Eye Tetra Is Actually For
Red Eye Tetra is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially plants.
The most common mistake is buying Red Eye Tetra for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
Red Eye Tetra Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Red Eye Tetra.
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
40 Gallon Breeder
Show 17 more tank sizes
Frequently Asked Questions About Red Eye Tetra
How big does Red Eye Tetra get?
Red Eye Tetra (Moenkhausia sanctaefilomenae) typically reaches a maximum adult size of approximately 7 cm. They have a compressed body shape and a moderate growth rate.
What tank size does Red Eye Tetra need?
A minimum aquarium volume of 75 litres and a tank length of at least 60 cm are recommended for Red Eye Tetra. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Red Eye Tetra need?
Red Eye Tetra thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 5.5 and 8.5, and a general hardness of 3–20 dGH. A moderate water flow is preferred.
Is Red Eye Tetra peaceful or aggressive?
Red Eye Tetra is classified as mostly peaceful with an aggression score of 3 out of 10. They are generally well-suited to peaceful community tanks.
How many Red Eye Tetra should be kept together?
Red Eye Tetra is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Red Eye Tetra have any special tank requirements?
Yes. Red Eye Tetra benefits from plants - densely covered in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 11, 2026
- Last updated
- May 11, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Red Eye Tetra
These fish are strong compatibility matches for Red Eye Tetra based on water preferences, temperament, adult size, and tank behavior.
Spotted Hillstream Loach
Gastromyzon punctulatus
Ideal Tank MatesWhite Cheeked Goby
Rhinogobius duospilus
Ideal Tank MatesReticulated Stingray (Teacup Ray)
Potamotrygon orbignyi
Ideal Tank MatesXenotilapia ochrogenys
Xenotilapia ochrogenys
Ideal Tank MatesTandanus Catfish
Tandanus tandanus
Ideal Tank MatesPetricola Catfish
Synodontis petricola
Ideal Tank MatesPlants That Suit Red Eye Tetra
These plants pair well with Red Eye Tetra based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Afzel's Anubias
Anubias afzelii
Anubias Barteri
Anubias barteri
Balansae
Cryptocoryne crispatula
Bonsai Rotala
Rotala indica
Broadleaf Crinum
Crinum natans
Broadleaf Sagittaria
Sagittaria latifolia
Fish Similar to Red Eye Tetra
Serpae Tetra
Hyphessobrycon eques
A striking, deep-red schooling fish known for its highly active nature. While hardy and beautiful, Serpae Tetras are notorious fin-nippers. This behavior is usually localized within their own pecking order if kept in large enough schools (8+), but they should never be housed with slow-moving or long-finned tank mates like Bettas, Angelfish, or Gouramis.
Bloodfin Tetra
Aphyocharax anisitsi
An extremely hardy and energetic schooling fish characterized by its silver body and striking bright red fins. As exceptionally active swimmers, they require plenty of horizontal swimming space. They are very adaptable to temperature and water parameters, making them a fantastic choice for beginners. Must be kept in groups to curb minor fin-nipping tendencies.
Brilliant Rummy-Nose Tetra
Hemigrammus bleheri
One of the tightest schooling fish in the aquarium hobby, known for their striking bright red faces and black-and-white horizontally striped tail fins. They are highly active and need plenty of horizontal swimming space. The intensity of their red 'nose' serves as an excellent biological indicator of water quality and stress; it fades significantly if water parameters drop or they feel insecure.
Rosy Finned Tetra
Hyphessobrycon rosaceus
A beautiful, deep-bodied tetra known for its reddish-pink hue and striking dorsal fin, which features a prominent black patch and white tip. They are peaceful, active schooling fish that thrive in heavily planted tanks with slightly acidic, soft water. Males frequently engage in harmless mock-battles by flaring their fins to establish hierarchy.
Lemon Tetra
Hyphessobrycon pulchripinnis
A peaceful, deep-bodied schooling tetra known for its translucent yellow coloration and striking black and yellow fins. They are robust and active, making them an excellent choice for planted community aquariums. Their colors intensify significantly in a well-established tank with a dark substrate and proper schooling numbers.
Green Fire Tetra
Aphyocharax rathbuni
The Green Fire Tetra is a lively, schooling fish originating from South America. They are characterized by their metallic green bodies and a striking red coloration on their lower flanks and anal fins. They are generally peaceful but highly active, requiring plenty of swimming space and a group of conspecifics to feel secure and display their best colors.