A peaceful, active schooling fish native to the Amazon basin. It is commonly called the 'Belgian Flag Tetra' due to the distinctive tricolor lateral stripe (black, red, and yellowish-white) running along its side. They are an excellent community fish that thrives in planted aquariums with soft, slightly acidic water. Like most tetras, they must be kept in groups to feel secure and display their best colors.
Flag Tetra At a Glance
Flag Tetra Tank Requirements
Will Flag Tetra fit in your tank?
Care guides tell you what Flag Tetra needs, the next question is whether your tank can safely provide it. Test Flag Tetra against your tank size, maintenance needs, and the fish you already keep before you buy.
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Flag Tetra Water Parameters
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Flag Tetra Temperament & Compatibility
Flag Tetra Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard form found in the aquarium trade. Highly social and best kept in schools of 6 or more (ideally 10+) to prevent stress, reduce shyness, and encourage tight shoaling behavior.
Same care requirements as the base species
Also known as: Belgian Flag Tetra, Wild Type
Flag Tetra Care Guide Summary
The Flag Tetra, scientifically known as Hyphessobrycon heterorhabdus, belongs to the Characins family group. Adults reach a maximum size of approximately 4.5 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the mid-level zone of the aquarium and produces a low level of biological waste.
To thrive, the Flag Tetra requires a freshwater only aquarium with a minimum volume of 55 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 5.5–7.5 and a general hardness of 2–12 dGH. A moderate water flow is preferred.
The Flag Tetra is a rewarding species to keep, provided its core environmental needs are met. The Flag Tetra is typically available in one standard form.
Flag Tetra Habitat Setup
When setting up an aquarium for the Flag Tetra, a moderate water flow best suits their natural preferences. Because this species occupies the mid-level zone, the aquarium layout should prioritise open swimming space in the centre of the tank for free movement. Useful additions include leaf litter or blackwater tannins to replicate their natural soft-water habitat and dense planting to provide cover, break sightlines, and reduce stress.
Flag Tetra Compatibility Notes
Classified as peaceful, the Flag 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, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the mid-level zone can help reduce competition and territorial overlap.
Flag Tetra Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Flag Tetra.
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
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Frequently Asked Questions About Flag Tetra
How big does Flag Tetra get?
Flag Tetra (Hyphessobrycon heterorhabdus) typically reaches a maximum adult size of approximately 4.5 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Flag Tetra need?
A minimum aquarium volume of 55 litres and a tank length of at least 60 cm are recommended for Flag Tetra. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Flag Tetra need?
Flag Tetra thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 5.5 and 7.5, and a general hardness of 2–12 dGH. A moderate water flow is preferred.
Is Flag Tetra peaceful or aggressive?
Flag Tetra is classified as peaceful with an aggression score of 1 out of 10. They are generally well-suited to peaceful community tanks.
How many Flag Tetra should be kept together?
Flag 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 Flag Tetra have any special tank requirements?
Yes. Flag Tetra benefits from plants - densely covered and leaf litter/blackwater in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Top Tank Mates for Flag Tetra
These fish are strong compatibility matches for Flag Tetra based on water preferences, temperament, adult size, and tank behavior.
Hillstream Loach
Beaufortia leveretti
Ideal Tank MatesSchwartz's Cory
Corydoras schwartzi
Ideal Tank MatesLeopard Cory
Corydoras leopardus
Ideal Tank MatesGold Laser Cory
Corydoras sp. 'CW010'
Ideal Tank MatesDainty Cory (Salt and Pepper Cory)
Corydoras habrosus
Ideal Tank MatesIncolicana Corydoras
Corydoras incolicana
Ideal Tank MatesPlants That Suit Flag Tetra
These plants pair well with Flag 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
Amazon Sword
Echinodorus amazonicus
Anacharis
Egeria densa
Anubias Barteri
Anubias barteri
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to Flag Tetra
Congo Tetra
Phenacogrammus interruptus
A stunning, large schooling fish native to the Congo River basin. Known for their iridescent rainbow colors and active swimming behavior. Despite their size, they are notoriously peaceful and can be skittish, requiring ample swimming space, dim lighting or floating plants, and peaceful tank mates. Avoid keeping with fin-nippers.
Bentos Tetra
Hyphessobrycon bentosi
A striking, deep-bodied tetra native to the slow-moving waters of the Amazon basin. Characterized by a reddish-brown tint and a prominent black spot on the dorsal fin, often tipped with white. They are active but peaceful schooling fish. Males will frequently engage in harmless, visually impressive sparring displays to establish hierarchy and impress females.
Neon Tetra
Paracheirodon innesi
One of the most iconic freshwater fish in the hobby, famous for its striking iridescent blue and red stripes. Originally from the blackwater streams of the Amazon basin, they prefer slightly cooler water than many tropical fish and must be kept in schools to thrive, display natural behaviors, and feel secure.
Blue Emperor Tetra
Inpaichthys kerri
The Blue Emperor Tetra, also known as the Royal Tetra, is a stunning, active schooling fish native to the Aripuanã River basin in Brazil. They feature a bold dark lateral stripe and vibrant blue-purple iridescence that intensifies in planted aquariums with slightly acidic water. Males will actively spar and display to establish dominance, but are harmless to other species.
Black Neon Tetra
Hyphessobrycon herbertaxelrodi
A peaceful, active schooling fish native to the Paraguay basin. Known for its striking contrast of a dark black lateral stripe underneath a glowing iridescent white/green-gold stripe. Excellent for community aquariums, particularly in planted setups or blackwater biotope tanks with subdued lighting.
Emperor Tetra
Nematobrycon palmeri
A striking, robust schooling fish from Colombia. Unlike many tetras, they do not swim in a tight shoal, preferring to loosely associate while males stake out small territories to display to females. They feature a bold black lateral line and iridescent purple/blue hues.