Description
The rummy-nose tetra is instantly recognisable: blazing red head and a black-and-white striped tail like a flag. But what makes it genuinely special is not the looks — it is that it tells you about the state of your tank.
The intensity of the red nose depends directly on water quality. If nitrate rises, if the filter is struggling, if something starts going wrong, the red fades — and often it fades before a test kit picks anything up. Keeping a shoal of rummy-nose is like having a sensor with fins: when they look pale, it is time to check the tank.
Worth knowing that the same mechanism works in reverse and misleads newcomers: freshly bought fish arrive pale from transport stress. They are not sick and you were not cheated. Within a few days, if the water is right, the nose lights up.
Behavior
It forms the tightest, most synchronised shoal of any tetra. A group of twelve swims as a single body, turning together. It is the fish that best demonstrates why a real shoal cannot be replaced with four scattered individuals.
Completely peaceful, though its energy is high. It swims fast and constantly, which can be overwhelming for very calm or slow species.
It lives well with cardinals and other Amazonian characins, corydoras, otocinclus, bristlenose and ram cichlids. It is one of the best companions for a planted Amazon biotope.
Avoid housing it with adult angelfish and large cichlids, on size; calm bettas and gouramis, which its constant activity stresses; and hard-water fish, since it needs soft and acidic.
With shrimp: adults are fine. Fry are not.
A note on tank size: litres alone are not enough, it needs length. An active shoal in a short, tall tank gets stressed even when the parameters are perfect.
Habitat
Hemigrammus rhodostomus comes from the lower Amazon and the Orinoco, soft acidic blackwater with gentle flow and leaf-littered beds. It lives in large shoals in open stretches of the channel, not hidden among plants.
Hence its need for horizontal space: it is a long-distance swimmer, not a corner dweller. And hence its sensitivity too, because the water in those rivers is very mineral-poor and very stable, without the swings of a poorly maintained tank.
The ideal setup is the classic Amazon one: leaf litter, wood, plants along the sides and an open centre so the shoal has somewhere to run.
Borrachito is a schooling species, which means that in the wild it lives and moves in large, coordinated groups.
Keep at least 8 individuals so they feel comfortable and their stress level stays low.
Habitats
Fish sharing this habitat
These fish appear in one or more habitats linked to this profile. It doesn't mean they are directly compatible in an aquarium.
Details
🌊 Water parameters
🐠 Minimum tank size
Breeding
Demanding and uncommon among hobbyists. It requires very soft, acidic water, dim light and a mature tank; spontaneous spawns in a community tank are rare and the eggs come to nothing.
It is an egg scatterer and does not tend the spawn. If you are serious about it, the setup is the same as for the cardinal: dedicated tank, very low conductivity, darkness and immediate separation of the adults.
As with the cardinal, do not treat it as a failure if you never see fry. In a normal aquarium it simply does not happen.
Diet
An uncomplicated omnivore, with a small mouth like the rest of the group.
- Staple: quality flake or fine micropellets.
- Supplement: frozen daphnia, brine shrimp and cyclops, two or three times a week.
- Fry: liquid food or infusoria at first.
One detail matters more here than usual: this fish shows the effects of overfeeding before any other. Uneaten food breaks down, nitrate rises and the nose fades. So the rule about removing leftovers within two minutes is not just hygiene — it is what preserves the very colour you bought the fish for.
What about your tank?
Enter your tank's values to see only the compatible species that fit them. Litres apply to fish.
Compatible fish
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 7 and 26–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–26 °C.
They share water: pH 6–7 and 24–25 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6.5–7 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–27 °C.
They share water: pH 6–7 and 25–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 5.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6–7 and 24–26 °C.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 5.5–7 and 26–27 °C.
They share water: pH 5.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 5.5–6.5 and 24–27 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 6–7 and 24–26 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
Compatible invertebrates
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 5.5–6.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–25 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 5.8–6.8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 5.8–6.8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–27 °C.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
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They share water: pH 7 and 24–27 °C. They only meet at the very edge, so the tank has to hold that value.
Sources
- FishBaseFroese, R. and D. Pauly. Editors. 2026. FishBase. World Wide Web electronic publication.
- Seriously FishSeriously Fish. Hemigrammus rhodostomus. Ficha de especie; consultada 2026-08.
Discrepancy: FishBase publishes no aquarium parameters for the species, so pH, temperature and hardness come from Seriously Fish (5.5-7, 24-27 °C, 2-15 dH).
Plan your next aquarium
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