Rummynose Tetra Care Guide

The rummynose tetra is the tightest-schooling fish in the common hobby — a silver torpedo with a blazing red nose and a candy-striped tail that moves as one with its school. The red face is more than decoration: it works as a live water-quality gauge, fading the moment conditions slip. Buy a proper crowd of them or you will never see what the fish is for.

Rummynose Tetra at a glance

The sourced figures the welfare engine uses to judge Rummynose Tetra — the parseable key facts.

Where it comes from

Rummynose come from the blackwater rivers and tributaries of the Amazon and Orinoco systems — soft, very acidic, tannin-stained, shaded forest waters. That origin sets the care: they thrive on tannins from botanicals and leaf litter, dim light and dark substrate; they sit comfortably at the warm end of the tropical range, which is why they pair with discus; and they are highly sensitive to ammonia, nitrite and to sudden swings, so a mature, stable tank is non-negotiable. One quirk worth knowing up front: "rummynose tetra" is a trade name covering three near-identical species, and the fish you actually buy is usually Hemigrammus bleheri, not the H. rhodostomus the name technically refers to. Care is the same across all three.

Did you know?

• It is a genuine scientific model organism: physics and biology labs study the rummynose to build mathematical models of how fish schools self-organise.
• Its red nose is a built-in water-quality gauge — the "canary in the coal mine" of the freshwater hobby, fading to pink the moment ammonia, nitrite, nitrate or a temperature swing appears.
• It swims in a burst-and-coast rhythm — short bursts then gliding — and copies its neighbours' turns, schooling largely by sight backed by flow sensing.
• Three fish, one name: the "rummynose" you buy is usually Hemigrammus bleheri, not the H. rhodostomus the name refers to, and a third "false" species hides in shipments, told apart by a missing tail-spot.
• A 2020 revision moved all three into the genus Petitella, so the true rummynose is now Petitella rhodostoma in FishBase — a taxonomy footnote, not a care change.

Tank size — and why

A 20 US gallon, roughly 90 cm footprint is the practical floor, and longer is markedly better — not for bio-load (these are small, low-waste fish) but because the entire point of the species is a fast, sweeping, synchronised school that needs an open swimming lane. A long footprint gives a tighter, more confident, more dramatic shoal; a short or tall tank wastes the fish. Leave an open central lane through the planting, prioritise length over height, and keep a lid — they are active swimmers, though not notorious jumpers.

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

Water parameters in practice

Soft, slightly acidic water is the target, and stability matters more than chasing an exact number — captive-bred stock tolerates up to neutral, but breeding needs genuinely soft, acidic water. The load-bearing point is sensitivity: rummynose are extremely intolerant of ammonia, nitrite and high nitrate, and of sudden shifts, so keep them in a mature, cycled tank only, with ammonia and nitrite reading zero and nitrate low. They sit at the warm end of the range and can be pushed toward the low 80s Fahrenheit for a discus tank. This nitrogen-sensitivity is exactly what makes the red nose a barometer, and what makes acclimation shock the number-one killer.

Diet & feeding

Omnivorous micro-predators that will eat almost anything offered, but with a small mouth, so foods must be small — a quality micro flake, nano pellet or crushed food as the staple, varied with baby brine shrimp, daphnia, microworm and bloodworm. Foods rich in krill or salmon deepen the red. Feed small amounts once or twice a day and feed sparingly, because these fish are nitrogen-sensitive and overfeeding fouls the water they most need kept clean. As active mid-water feeders in a group they dart for food, so make sure the school gets its share against faster or larger tankmates.

Gear & setup

A heater for the warm setpoint, gentle-to-moderate filtration, and a planted layout with an open swimming lane. Dark substrate intensifies the red and lowers stress; driftwood, botanicals and leaf litter tint the water and suit the blackwater biotope. They handle a little current but come from soft-water tributaries, so avoid a torrent. A mature, well-cycled filter matters more here than for most tetras, because the whole species runs on stable, clean water.

Temperament & behaviour

Peaceful and obligate-shoaling, famous as the most synchronised schooler of the common tetras — it is even a scientific model species for collective behaviour, swimming in a burst-and-coast rhythm and schooling largely by sight backed by flow sensing. The behaviour collapses in small numbers: under-grouped fish are skittish, pale-nosed and stressed, while a big school produces the dramatic synchronized swarm the fish is bought for. It is not territorial and not a fin-nipper, but it will not compete well with boisterous or much larger tankmates.

Group & social needs

Keep ten or more — twelve to fifteen is ideal. Authoritative sources call for groups of ten or preferably more, and the species' entire appeal is the tight school, so six is a poor floor that undersells both its welfare and its behaviour. Larger groups school more dramatically, hold a deeper nose colour and dilute individual stress. If you only have room for a handful, this is the wrong fish.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Rummynose 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.
• Bamboo Shrimp (Wood/Fan Shrimp) — Peaceful temperament, similar adult size.
• Black Neon Tetra — Peaceful temperament, similar adult size.

A note on the shrimp and snails here: Rummynose 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.

See the full Rummynose Tetra tank mates guide →

Breeding & sexing

Sexing is subtle — mature females are noticeably rounder-bodied than the slimmer males. Breeding is moderate-to-advanced, among the harder small tetras because of the strict water chemistry: a separate spawning tank with very soft, acidic water (around pH 5.5–6.5, very low hardness) kept warm and dim, with fine-leaved plants or a spawning mop for the scattered eggs, and the pair conditioned on live foods first. They scatter eggs and eat them, so remove the adults afterwards. Eggs hatch in roughly a day or two and the fry, raised on infusoria then microworm and baby brine shrimp, need dim, pristine conditions.

Lifespan

Five to six years is typical, with up to about eight reported under excellent care. The dominant factor in early death is water-quality instability and acclimation shock — most sudden losses trace to moving fish too fast between different water, or to an uncycled tank. Chronically poor water, too-small a group and stress-driven ich take the rest. Settled in stable water, a rummynose is a durable, long-lived fish; freshly imported into a new tank, it is among the more delicate tetras.

Common mistakes

• Adding them to a new or uncycled tank — the number-one killer. They are highly nitrogen-sensitive and new-tank instability causes most early deaths; use a mature tank only.
• Rushing acclimation. Moving them fast between different water causes acclimation shock and sudden death — drip-acclimate them.
• Buying too few. A group of four to six gives skittish, pale-nosed, poorly-schooling fish; buy ten or more, twelve to fifteen for the real behaviour.
• Ignoring a faded nose. A pale nose is a water-quality alarm, not a cosmetic quirk — test the water when you see it.
• Housing them with predators or large, aggressive fish that can eat or out-compete a 5 cm tetra, including big or aggressive angelfish.

Signs of trouble

• A pale or faded nose across the school — the first and most reliable warning sign; test for ammonia, nitrite, nitrate and a temperature swing.
• Loss of schooling cohesion, with fish scattering or hiding rather than moving as one — stress or deteriorating water.
• White spots and flashing or rubbing on décor — ich, to which stressed rummynose are prone.
• Clamped fins and listlessness in new arrivals — acclimation stress; settle them slowly and keep the tank stable.

Is this fish right for you?

Do not buy rummynose unless your tank is fully cycled and mature — they are not a fish to cycle a tank with. Skip them if you cannot keep a group of ten or more, if you cannot provide soft, warm, stable water, or if your community holds anything big enough to eat a 5 cm tetra. In the shop, judge the stock by the noses: a tank of bright-red, tightly-schooling fish is healthy, while pale-nosed, scattered fish signal stress or sickness — buy elsewhere. Avoid "platinum" or dyed novelty morphs if welfare matters to you.

Bringing one home

Rummynose are very sensitive to parameter jumps, so acclimate slowly and deliberately — float to match temperature, then drip or add tank water a little at a time over a good half hour before netting the fish across and leaving the shop water behind. Expect the noses to fade during transport and for a day or two afterwards; that acclimation fade is normal, so give them time in a mature, stable tank before assuming a problem, and quarantine new stock.

Common questions

Why are my rummynose tetras' noses pale?

A faded nose is a stress and water-quality alarm. The usual triggers are ammonia or nitrite above zero, high nitrate, a temperature swing, recent transport, bullying or illness. Test the water and check temperature first. A fade for a day or two after buying or a water change is normal acclimation and recovers on its own.

How many rummynose tetras should I keep?

Ten or more, with twelve to fifteen ideal. They are the tightest-schooling common tetra, and small groups stay skittish and pale-nosed; the dramatic synchronised swarm only appears in a real crowd. Treat six as a poor floor, not a goal.

Are rummynose tetras hardy or good for beginners?

They are hardy once settled in stable water, but fragile during acclimation and in new tanks — among the more delicate tetras to establish. They suit a patient keeper with a mature, cycled, soft, warm tank, not a brand-new setup.

Can rummynose tetras live with discus or angelfish?

They are a top discus tankmate — they tolerate the heat and soft acidic water, are large enough not to be eaten, and their bold schooling acts as a dither fish that reassures shy discus. With angelfish it is conditional: fine as a dither fish, but risky with large or aggressive angels, so judge by size and temperament.

What is the difference between H. bleheri and H. rhodostomus rummynose?

They are near-identical and kept the same way. The common firehead, H. bleheri, has the reddest face, with red extending beyond the gill covers onto the shoulder. The true rummynose, H. rhodostomus, has a less extensive red head and a clear tail-spot; a third species, Petitella georgiae, lacks that tail-spot.

Sources & confidence

Sources & confidence (9 species)

These back the Rummynose 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.

• Rummynose Tetra Hemigrammus rhodostomus — Seriously Fish (seriouslyfish.com/species/hemigrammus-rhodostomus) high confidence
• Amano Shrimp Caridina multidentata — Aquarium Co-Op amano shrimp care; Aquadiction high confidence
• Bamboo Shrimp (Wood/Fan Shrimp) Atyopsis moluccensis — Aquariadise (aquariadise.com/caresheet-bamboo-shrimp-atyopsis-moluccensis) 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
• Bleeding Heart Tetra Hyphessobrycon erythrostigma — Seriously Fish (Hyphessobrycon erythrostigma) high confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) 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 — Petitella rhodostoma (Hemigrammus rhodostomus) — authority (Ahl 1924), max 5 cm TL, lower Amazon and Orinoco range, trophic level, 2020 reclassification to Petitella, diagnostic features, group husbandry
• Seriously Fish — Hemigrammus rhodostomus — blackwater biotope and chemistry, 90 cm minimum tank, temperature/pH/hardness, "groups of 10 or preferably more," small-food diet, peaceful temperament, sexing and breeding parameters
• Seriously Fish — Hemigrammus bleheri — the firehead, "most commonly sold as rummy-nose tetra," Rio Negro/Meta range, distinguishing red beyond the gill covers, parameters and group needs
• Aquarium Co-Op — Rummy-Nose Tetras — 20 gal+, warm tolerance to the low-80s °F, school of 8–12 (15+ best), krill/salmon foods for colour, the red nose as "canary in the coal mine," tank mates and lifespan
• Royal Society / collective-behaviour research (Hemigrammus rhodostomus) — model-species status for schooling, burst-and-coast intermittent swimming, vision-plus-flow sensing, illuminance threshold and phalanx formation
• Red-nose / water-quality indicator hobby consensus — nose-fade triggers (ammonia/nitrite/nitrate, temperature swings, transport), normal acclimation fade, and using the nose as an early-warning system
• Lifespan, health and acclimation hobby consensus — 5–6 year lifespan (up to ~8), ich susceptibility, ammonia/nitrite sensitivity, "mature tanks only," and acclimation shock as the leading cause of sudden death

More on Rummynose Tetra

Related guides on TankStocking — each scored by the same welfare engine as the planner.

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 →