Flame Tetra (Von Rio Tetra) Care Guide

The flame tetra, or Von Rio, is one of the genuinely easy tetras — hardy, peaceful, cheap and unusually cool-tolerant, a textbook beginner schooler that largely looks after itself in a planted group. The twist that makes it special: the fish you buy is thriving in captivity while its wild ancestors have all but vanished, so here it is the tank-bred fish, not the wild one, that is the responsible choice.

Flame Tetra (Von Rio Tetra) at a glance

The sourced figures the welfare engine uses to judge Flame Tetra (Von Rio Tetra) — the parseable key facts.

Where it comes from

Hyphessobrycon flammeus comes from a small, near-coastal stretch of south-east Brazil — the Rio de Janeiro area (Guanabara Bay, the Paraíba do Sul and Guandu basins) and the upper Tietê of São Paulo, hence the trade names Rio and Von Rio. Its home is shallow tributary streams under half a metre deep, slow-flowing, vegetated and shaded, with clear-to-brownish water over sand. That subtropical coastal origin is the whole care sheet: the streams swing cooler than the Amazon, which is why the flame tetra tolerates cool rooms and was historically the go-to fish before reliable heaters; the wide natural hardness band is why it adapts to ordinary tap water rather than demanding blackwater; and the slow, shaded, planted habitat is why it colours up best over dark substrate in gentle flow and dislikes strong current.

Did you know?

• Your aquarium fish is thriving while the wild fish is vanishing. H. flammeus is assessed by the IUCN as Endangered (assessed November 2018), with the last confirmed wild record from Rio de Janeiro state in 1992 and much of its tiny range lost to habitat destruction, pollution and introduced tilapia and black bass — yet it stays common and cheap in the hobby because it is mass-bred in captivity, making tank-bred stock the low-impact, ethical pick.
• It was famous before it had a name. C. Bruening of Hamburg imported it to the hobby in 1920, four years before George S. Myers formally described it as Hyphessobrycon flammeus in 1924.
• The 'before-heaters' beginner fish. Its cool tolerance made it a staple in the early-to-mid-20th-century hobby, when reliable aquarium heaters were not standard and a fish that handled cool rooms was the obvious choice.
• Named for Rio. The trade names Rio and Von Rio come straight from its type locality, Rio de Janeiro.
• Easy to sex for a tetra — the black-tipped anal and pelvic fins on males give it away at a glance.

Tank size — and why

A 15 US gallon, roughly 60 cm footprint is the practical floor for a proper school, and bigger is better. The driver is not bioload — these are tiny, low-waste fish — but swimming room and group size. Flame tetras are active mid-water schoolers that need a lateral lane to move as a group, so prioritise footprint over height: a long, planted base beats a tall column, with a 60 cm-plus length giving the tight school it wants. A lid is sensible, as startled small tetras can jump, though they are not notorious jumpers.

As a guide, a 20-gallon tank comfortably suits about 8–11 Flame Tetra (Von Rio Tetra) as a single-species display, leaving room for tankmates.

See it to scale

Adult Flame Tetra (Von Rio Tetra) reach only about 4 cm (1.6 in) long — close to the size they are sold at, so what you see is roughly what you get. The catch is the group: a proper shoal still needs about a 15-gallon tank, around 51 cm long.

Adult size is sourced; tank length is approximate for a standard 15-gallon aquarium.

Water parameters in practice

This is one of the more forgiving tetras. Aim for about 22-26 °C and a near-neutral pH of roughly 6-7, but the headline is breadth: it handles a wide hardness band and ordinary tap water far better than a cardinal or neon, and only needs soft, acidic water for breeding. The standout trait is cool tolerance — sources put the survivable band at roughly 18-29 °C, and its subtropical origin means it copes with cool rooms that would stress most tropical tetras. Do not overstate this, though: it is not a coldwater fish. Chronic cold stresses it and invites ich, so keep it in the low-to-mid 20s for best health and treat the cool tolerance as a safety margin, not a target. As ever, stability beats chasing perfect numbers, and abrupt swings are what it dislikes most.

Diet & feeding

An unfussy omnivore and micropredator — in the wild it takes small insects, worms, tiny crustaceans, filamentous algae and detritus. A good-quality micro flake or crushed nano pellet makes the staple; vary it with small live or frozen foods such as bloodworm, mosquito larvae, daphnia, cyclops and baby brine shrimp to condition for breeding and deepen the red (brine shrimp in particular is noted to boost colour). Feed small amounts once or twice a day — roughly what they clear in a few minutes — as the tiny stomachs mean overfeeding fouls the water faster than it helps. As mid-water feeders they dart for food, so make sure their share reaches them past faster tankmates.

Gear & setup

Undemanding on kit. A heater to hold a stable setpoint (it tolerates cool rooms but still wants steady warmth), a gentle filter delivering modest flow rather than a strong current — these are slow-stream fish that tire and stress in fast water — and a planted layout. Dark or sandy substrate intensifies the red and mimics the shaded stream bed; plant heavily around the sides and back with an open swimming lane at the front, and add floating plants for shade, driftwood and leaf litter for tannins. Keep it covered, but jumping is a minor concern.

Temperament & behaviour

A peaceful shoaling mid-water fish that is community-safe in normal settings and not a true fin-nipper. There is one nuance that sets it apart from a totally placid fish like the cardinal: males form temporary dominance hierarchies and spar for status. In a proper group this is harmless display that actually brings out their best colour, but in too small a group it can curdle into real aggression, with a dominant male targeting the others. The behaviour only looks right in numbers — a tight, confident, vividly coloured school versus skittish, washed-out and occasionally nippy fish when under-stocked.

Group & social needs

Keep a real group. Five is the bare floor cited by FishBase and six the common hobby minimum, but Seriously Fish recommends eight to ten and that is the target to aim for. Larger groups dilute the male sparring, cut stress and produce the tight, bold, colourful schooling the fish is bought for. Treat the peacefulness as conditional on numbers: an under-stocked group of three or four is exactly where the male aggression and fading show up.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Flame Tetra (Von Rio Tetra) and that suit its size and temperament best. Tap any to load the pairing in the planner.

• Amano Shrimp — Peaceful temperament, similar adult size.
• Assassin Snail — Uses the bottom zone, peaceful temperament, similar adult size.
• Black Neon Tetra — Peaceful temperament, similar adult size.

A note on the shrimp and snails here: Flame Tetra (Von Rio Tetra) is peaceful and generally invertebrate-safe — but almost any fish will take very small shrimplets given the chance, so give shrimp dense cover (moss, leaf litter) if you want a colony to grow, rather than expecting every baby to survive.

This engine-cleared shortlist is Flame Tetra (Von Rio Tetra)'s tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Sexing is easy for a tetra — males are slimmer, more intensely coloured and carry black-tipped anal and pelvic fins plus tiny bony hooks on those fins; females are deeper-bodied, larger and paler, with a curved anal fin and no black tips. Breeding is rated easy-to-moderate, one of the more beginner-accessible egg-scattering tetras. Use a separate dimly-lit spawning tank with fine-leaved plants, a spawning mop or a mesh base to protect the eggs, soften and acidify the water to around pH 5.5-6.0 and very low hardness, and raise the temperature to about 26-28 °C, conditioning the pair on live foods first. They scatter eggs, give no parental care and will eat their own spawn, so remove the adults afterwards. Females drop somewhere from a couple of hundred up to several hundred eggs; these hatch in roughly one to two days and the fry are free-swimming a few days later, raised on infusoria then microworm and baby brine shrimp.

Lifespan

Three to five years is normal in a well-kept tank, with FishBase giving a longevity of around four years. What shortens it is chronic poor water quality, too small a group, strong current that tires them, abrupt temperature or parameter swings, and ich brought on by chronic cold or stress. Hormone-treated or dye-injected imports are also shorter-lived, as the treatment lowers their ability to fight disease.

Common mistakes

• Keeping too few. One to five fish stress and fade, and this is the rare tetra where males turn aggressive on each other when under-stocked — buy six minimum, eight to ten or more for a calm, colourful school.
• Mistaking cool-tolerant for coldwater. They survive cool rooms but are still tropical; chronic cold invites ich, so hold them in the low-to-mid 20s for best health.
• Strong current. These are slow-stream fish that tire in high flow — use gentle filtration.
• Fast, nippy or large tankmates. Tiger barbs, serpae tetras and big cichlids out-compete, nip or eat them.
• Confusing them at the shop with the serpae or 'red minor' tetra (Hyphessobrycon eques) — a deeper, all-over blood-red fish with a dark shoulder spot and a known fin-nipper. The flame is two-toned orange and far more peaceful.
• Buying hormone- or dye-treated 'enhanced' stock. Colour-injected imports are a welfare red flag and shorter-lived; buy naturally-coloured, ideally captive-bred fish.

Signs of trouble

• Colour fading and a fish hanging apart from the school — usually water quality, an immature tank, or too small a group.
• One male relentlessly chasing the others — an under-stocking signal; add numbers and cover.
• A curved or kinked spine, whitish subcutaneous patches and erratic swimming — neon tetra disease, the same incurable microsporidian that affects neons and cardinals (the genus is a known host); remove the fish promptly.
• Flicking and scratching against decor — early ich (white spot), often triggered by chilling or stress.
• Clamped fins, hiding and erratic swimming after a recent change — general stress, often from strong flow or an abrupt parameter swing.

Is this fish right for you?

Don't buy flame tetras if you can't keep a group of at least six (eight to ten is better), if your tank is under about 15 gallons or 60 cm, if you run a high-flow setup, or if your community contains aggressive fin-nippers or predators their size. On sourcing, the right call is the opposite of the cardinal: because wild Hyphessobrycon flammeus is IUCN Endangered and almost every fish in the trade is mass captive-bred, choosing tank-bred stock is both the hardier and the more responsible choice — be sceptical of any 'wild-caught' claim for this species, and avoid hormone- or dye-treated imports entirely.

Bringing one home

Add flame tetras only to a mature, cycled, stable tank, and acclimate gently — float the bag to match temperature, then add tank water a little at a time over fifteen to twenty minutes before netting the fish across and leaving the transport water behind. They cope with a wide range but dislike abrupt swings, so a slow transfer and a settled tank matter, and quarantining new stock guards against ich and neon tetra disease.

Common questions

Are flame tetras good for beginners?

Yes — they are among the hardier, more adaptable tetras, cope with ordinary tap water and even cool rooms, and quickly settle into most tropical setups. The one caveat is to buy a proper group of six or more, since under-stocked males can spar.

How many flame tetras should I keep?

Six is the bare minimum; eight to ten or more is the real target. They form male dominance hierarchies, and in too small a group that competition can turn into real aggression as well as faded colour — bigger groups stay calm, bold and bright.

Can flame tetras live in a cold or unheated tank?

They tolerate cooler water than most tropical tetras (roughly down to 18-20 °C) thanks to their subtropical Rio de Janeiro origin, which is why they suit cooler rooms. But they are not a coldwater fish — chronic cold stresses them and invites ich, so keep them stable in the low-to-mid 20s.

What is the difference between a flame tetra and a serpae (red minor) tetra?

The flame is two-toned — silvery front with two dark bars, flame-orange rear — and peaceful. The serpae is a deeper, all-over blood-red fish with a dark shoulder spot and a known fin-nipper. They are routinely confused in shops, so check the colour pattern before you buy.

Should I buy wild-caught or captive-bred flame tetras?

Captive-bred, without question. Wild H. flammeus is IUCN Endangered with a tiny, collapsing range, while almost all trade fish are mass tank-bred — so the captive-bred fish is both hardier and the ethical choice, the opposite of the cardinal tetra's situation.

Sources & confidence

Sources & confidence (9 species)

These back the Flame Tetra (Von Rio Tetra) figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Flame Tetra (Von Rio Tetra) Hyphessobrycon flammeus — AquaInfo / Aquarium Wiki (Hyphessobrycon flammeus) high confidence
• Amano Shrimp Caridina multidentata — Aquarium Co-Op amano shrimp care; Aquadiction high confidence
• Assassin Snail Clea helena (Anentome helena) — The Shrimp Farm (theshrimpfarm.com/posts/assassin-snail-care) high confidence
• Black Neon Tetra Hyphessobrycon herbertaxelrodi — Seriously Fish / Aqua-Fish (Hyphessobrycon herbertaxelrodi) high confidence
• Black Phantom Tetra Hyphessobrycon megalopterus — Seriously Fish (Hyphessobrycon megalopterus) high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Bronze Corydoras Corydoras aeneus — Seriously Fish (seriouslyfish.com/species/corydoras-aeneus) high confidence
• Cardinal Tetra Paracheirodon axelrodi — Seriously Fish (seriouslyfish.com/species/paracheirodon-axelrodi) high confidence
• Celestial Pearl Danio Celestichthys margaritatus — Seriously Fish (seriouslyfish.com/species/celestichthys-margaritatus) high confidence

Care-guide sources (7)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• FishBase — Hyphessobrycon flammeus — authority (Myers 1924), max 2.6 cm SL, temp 22-28 °C, pH 5.8-7.8, dH 5-25, Rio de Janeiro/Paraíba do Sul/Guandu/upper Tietê range, 'thought to be extinct in the wild', longevity ~4 yr, fecundity 200-330 oocytes, eggs hatch 2-3 days, IUCN Endangered assessed 2018, groups of 5+/60 cm husbandry
• Seriously Fish — Hyphessobrycon flammeus — family Characidae, no synonyms, trade names, biotope (sub-50 cm shaded streams), wild water 20-26 °C / pH 5.5-7.5 / 18-215 ppm, 20-25 mm SL, 60×30 cm minimum, group 8-10, male dominance hierarchies, sexing (bony hooks, black fin tips), egg-scatterer breeding, Brazilian threatened status
• Wikipedia — Flame tetra — Myers 1924 description and 1920 Bruening import, native range, ~2.5 cm, colour pattern and male black fin tips, IUCN Endangered plus Brazilian red list, threats (habitat loss/pollution/tilapia/black bass), last Rio record 1992, captive-bred trade, gold/orange/albino forms
• Aquarium Source — Flame Tetra Care — 1-1.6 in size, 3-5 yr lifespan, hardy/beginner ('quickly adapt to most tropical tank conditions'), 15 gal minimum, temp 64-85 °F (ideal 72-82), pH 5.5-7.5, 3-15 dGH, three-minute feeding rule, group 6+, sexing, breeding (500+ eggs, hatch 1-2 days), ich/bacterial risks, common mistakes
• AquaInfo — Hyphessobrycon flammeus (Flame Tetra) — 3-4 cm total, temp 20-24 °C with a caveat against extremes, pH 6.0-7.5, GH 4-12, 60 cm minimum, group 6-8, 'quiet peaceful fish' and under-stocking aggression note, Artemia boosts red, breeding (26-28 °C, pH 5.5-6, dH 1-5, hatch 24-36 h, infusoria fry)
• Fishkeeping World — Flame Tetra Care Guide — 2.5 cm, 3-5 yr, peaceful but 'easily stressed', adaptable, ideal 72-82 °F / tolerable 64-85 °F, pH 5.5-7.5, 3-15 dGH, 15 gal for 6-7 fish, group 6+, good/bad tankmates, detailed sexing, breeding (maturity 6-12 mo, 80 °F spawn), anti-hormone-treatment warning
• BuildYourAquarium — Flame Tetra cool-tolerance consensus — tolerance 64-85 °F, ideal 72-82 °F, 'not truly a coldwater fish', cold stress raises ich risk, and the historical pre-heater go-to framing (used to corroborate cool tolerance, not as a sole numeric source)

More on Flame Tetra (Von Rio Tetra)

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This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →