Hemigrammus rhodostomus
The benchmark schooling fish, moves as a single organism. Bright red nose is a real-time water-quality gauge: fades when stressed, glows when content. Wants clean, slightly soft water and the company of 10+ of its own kind.
Rummynose Tetra (Hemigrammus rhodostomus) reaches 4.5–5.5 cm as an adult and needs a minimum tank of 75 L. Native to Lower Amazon basin, Brazil, it lives in the mid water column with a peaceful temperament. Aim for 22–27 °C, pH 5.5–7.0, and 2–8 dGH hardness. Lifespan is 5–8 years with good care. Keep rummynose tetra in groups of 10+, yes (tight shoal) schoolers need numbers to display natural behaviour. Diet: omnivore, Crushed flake, micro pellets, frozen daphnia, baby brine shrimp. Plant-safe: Yes. Shrimp-safe: Mostly (may eat shrimplets).
Care at a glance
The benchmark schooling fish, moves as a single organism. Bright red nose is a real-time water-quality gauge: fades when stressed, glows when content. Wants clean, slightly soft water and the company of 10+ of its own kind.
Updated 3 min read
Part of our complete guide to aquarium fish for the planted tank.
Something looking off? Spot and treat it in our fish and shrimp health guide.
Hero photo by Gavinevans · CC BY-SA 3.0 · Wikipedia
The parameters that decide whether rummynose tetra fits in your tank.
Mid
Yes
Group of 10+
Characidae
Omnivore
Crushed flake, micro pellets, frozen daphnia, baby brine shrimp.
5–8 yrs
Hard
Soft acidic igapó forest streams of the Rio Negro
Lower Amazon basin, Brazil
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Cardinal tetras, otocinclus, corydoras, German blue rams, sterbai corydoras, sparkling gouramis, plant-safe peaceful fish at similar parameters.
Aggressive cichlids, fin-nippers, anything over ~8 cm. Skittish around larger or boisterous tank mates and will lose colour.
Weighing it against something similar? Compare Rummynose Tetra head to head:
Hard-won lessons from the tank.
Acclimate over 90+ minutes via drip — abrupt parameter shifts wipe the red instantly. Once you have a stable colony, the red nose is a free water-quality monitor: routine ammonia spikes show on the fish before they show on a test kit. Pair with a school of cardinal tetras for one of the most cinematic Amazon biotope displays in the hobby.
Genus 'Hemigrammus' = 'half-line' (referring to the lateral-line scale pattern). Species 'rhodostomus' = 'red mouth' in Greek. Sometimes called 'firehead tetra' even though that name technically belongs to H. bleheri.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Sensitive to ammonia and nitrate shifts — they show parameter trouble by losing the red on the nose before behaviour changes. Susceptible to ich during transport. Quarantine and observe red intensity for 4 weeks.
Often sold mixed across the three lookalike species. Often kept in groups too small (6–8) where shoaling behaviour doesn't trigger. They're not delicate — they're parameter-sensitive, which is different.
The practical routine, read top to bottom.
75 L+ for a meaningful shoal; 150 L+ is where they look stunning. Heavily planted with open swimming space along the length of the tank. Dark substrate, driftwood, catappa leaves. Gentle directional current — they orient against it and shoal beautifully. Sponge or canister filter; no powerheads.
4 weeks. Watch the nose. If it fades and stays faded, something is wrong even when behaviour looks normal.
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
See where the Rummynose Tetra and every other species comes from on the species world map.
Slow-moving, tannin-stained tributaries of the lower Amazon basin in Brazil. Soft, warm, acidic blackwater (pH 5.5–6.5 in the wild) with abundant leaf litter and submerged wood. They occur in absolutely massive shoals — thousands of fish moving as one.
Tiny crustaceans, mosquito larvae, fallen insects, biofilm. Continuous low-volume grazing.
Project Piaba (Brazil) sustainably wild-harvests them in the Rio Negro — buying 'wild Brazil' rummynose funds rainforest preservation. Czech and SE Asian farmed stock is also widely available.
How they pair, reproduce, and grow.
Females noticeably fuller-bodied when conditioned, especially viewed from above. Males slimmer with brighter colour. Hard to sex with confidence outside breeding condition.
Very difficult in home tanks. Egg scatterers — adults consume their own eggs. Soft (<2 dGH), acidic (pH 5.0–6.0), tannin-rich water; gradual temperature increase to 27 °C; dim lighting. Spawning mop or fine Java moss. Fry are extremely tiny — infusoria for the first 10 days. Almost all trade stock is wild-caught from Brazil's Project Piaba or farmed in Czech Republic and Indonesia.
The named cultivars and the lookalikes worth flagging.
Three species commonly sold as 'rummynose': H. rhodostomus (true rummynose, the standard), H. bleheri (firehead tetra, brightest red, most common in trade), and Petitella georgiae (false rummynose, slightly different black-banded tail). All three look nearly identical and have identical care — they're sold mixed constantly.
Direct answers to the questions search engines and AI assistants surface most often about this species.
Rummynose Tetra (Hemigrammus rhodostomus) needs a minimum tank of 75 L. They live in the mid water column and should be kept in groups of 10+, so a longer footprint matters more than depth.
Target 22–27 °C, pH 5.5–7.0, and 2–8 dGH hardness. Acclimate slowly when moving them between water sources.
Shrimp safety: Mostly (may eat shrimplets). Plant safety: Yes.
Rummynose Tetra are omnivore. Crushed flake, micro pellets, frozen daphnia, baby brine shrimp.
On Fin & Stem's 1–5 difficulty scale this species rates 3/5. Intermediate, stable parameters and a mature tank matter. Breeding difficulty: hard.
Typical lifespan in a well-maintained tank is 5–8 years.
A planted tank is a system. Pair this fish with one entry from each other pillar to plan the whole scape.
