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Description
Axelrodia riesei, the ruby tetra, is a tiny characid of about 2 cm, known only from the upper Meta River, in Colombia, within the Orinoco system. In nature it is an intense red, but the colour fades over time in the aquarium. It is said to inhabit blackwater and, given its size and demands, it is a poor community fish.
It is seen less than its relative A. stigmatias, which has a more elongated body and a silvery yellow colour: the species has a small, remote range. It is a fish for a tank of soft, acidic water, with dim light and leaf litter.
Behavior
Peaceful with other species, but not a good community fish because of its size and sensitivity. The ideal is to keep it alone or, at most, with diminutive, peaceful characins and small bottom catfish. It is gregarious, a loose group rather than a tight school, with rival males forming small territories and sparring regularly. The minimum is eight or ten fish: that way it is less shy and shows more.
It lives well with diminutive, peaceful characins and small callichthyids or loricariids.
Avoid housing it with lively or larger fish.
It must not go into a tank that has not matured.
Habitat
Axelrodia riesei lives in the upper Meta River basin, east of Villavicencio, in Colombia, a tributary of the Orinoco system. It is said to inhabit blackwater, though detailed information is lacking; it presumably occupies small, forested tributaries rather than the larger channels.
Axelrodia riesei 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.
Details
🌊 Water parameters
🐠 Minimum tank size
Breeding
It has been bred, and in a mature, well-structured aquarium a few fry may appear without intervention. It asks for soft, slightly acidic water and fine-leaved plants, such as Taxiphyllum, in which it spawns; leaf litter helps, because of the microorganisms that feed the fry. Once in condition, the adults spawn daily.
Diet
A micropredator of small invertebrates and zooplankton.
- Staple: very small dry food and brine shrimp nauplii.
- Supplement: daphnia, moina and grindal worm, live or frozen, daily.
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 5–7 and 24–28 °C.
They share water: pH 6–7 and 22–27 °C.
They share water: pH 5–7 and 23–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 5–7 and 20–26 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 5.5–7 and 23–28 °C.
They share water: pH 5.5–7 and 23–28 °C.
They share water: pH 6–7 and 20–25 °C.
They share water: pH 6–7 and 24–26 °C.
They share water: pH 6–7 and 22–27 °C.
They share water: pH 6–7 and 22–27 °C.
They share water: pH 6–7 and 22–27 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 22–26 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 6–7 and 21–26 °C.
They share water: pH 5.5–7 and 20–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 25–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6–7 and 22–26 °C.
They share water: pH 6–7 and 20–25 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6.5–7 and 20–24 °C.
They share water: pH 5–7 and 27–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 20–28 °C.
They share water: pH 6–7 and 22–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 20–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 22–28 °C.
They share water: pH 6–7 and 25–28 °C.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 5–7 and 22–28 °C.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 5.5–7 and 24–28 °C.
They share water: pH 6–7 and 26–28 °C.
They share water: pH 5–7 and 23–28 °C.
They share water: pH 5.5–7 and 23–28 °C.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 5.5–7 and 22–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 5.5–7 and 24–28 °C.
They share water: pH 6–7 and 22–26 °C.
They share water: pH 5.5–7 and 20–26 °C.
They share water: pH 4–6.5 and 23–27 °C.
They share water: pH 6.5–7 and 22–26 °C.
They share water: pH 6–7 and 20–26 °C.
They share water: pH 6.5–7 and 22–26 °C.
They share water: pH 6.5–7 and 22–26 °C.
They share water: pH 6.5–7 and 22–26 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 20–22 °C.
They share water: pH 6.5–7 and 20–24 °C.
They share water: pH 4.5–7 and 22–28 °C.
They share water: pH 4–7 and 23–28 °C.
They share water: pH 5–7 and 21–27 °C.
They share water: pH 4–7 and 22–28 °C.
They share water: pH 7 and 20–26 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 7 and 22–27 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 5.6–7 and 22–26 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 5.5–7 and 26–28 °C.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 5.5–7 and 22–26 °C.
They share water: pH 6.5–7 and 22–26 °C.
They share water: pH 6–7 and 25–28 °C.
They share water: pH 4.5–6.5 and 24–28 °C.
They share water: pH 5.5–7 and 24–28 °C.
They share water: pH 5.5–7 and 23–28 °C.
They share water: pH 5–7 and 23–27 °C.
They share water: pH 5–7 and 20–28 °C.
They share water: pH 5.5–7 and 23–28 °C.
They share water: pH 5.5–7 and 24–28 °C.
They share water: pH 6–7 and 20–26 °C.
They share water: pH 5.5–7 and 23–27 °C.
They share water: pH 6–7 and 22–26 °C.
They share water: pH 6–7 and 22–28 °C.
They share water: pH 5.5–7 and 24–27 °C.
They share water: pH 5.5–7 and 22–27 °C.
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 20–28 °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 20–24 °C.
They share water: pH 6.5–7 and 22–27 °C.
They share water: pH 7 and 20–25 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 20–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 7 and 22–28 °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 20–24 °C.
They share water: pH 5.8–6.8 and 20–24 °C.
They share water: pH 6.5–7 and 20–27 °C.
They share water: pH 6.5–7 and 22–28 °C.
They share water: pH 7 and 20–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 23–28 °C.
They share water: pH 6.5–7 and 23–28 °C.
They share water: pH 7 and 23–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 20–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 6.5–7 and 20–26 °C.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 22–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 20–28 °C.
They share water: pH 7 and 20–28 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7 and 20–28 °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 20–24 °C.
Sources
- FishBaseFroese, R. and D. Pauly. Editors. 2026. FishBase. World Wide Web electronic publication.
- Seriously FishSeriously Fish. Axelrodia riesei. Ficha de especie; consultada 2026-10.
Water: FishBase gives pH up to 7.0 (no minimum), hardness up to 8 dH (no minimum) and 20-26 °C; Seriously Fish, pH 4-6.5, 1-5 dGH and 20-28 °C. The widest range is used, pH (4-7), hardness (1-8) and temperature (20-28) included. Size: 2.1 cm SL in FishBase, which cites up to 4 cm TL, and 20 mm SL in Seriously Fish. Tank: Seriously Fish asks for a base of 60 × 30 cm (54 l). Name «ruby tetra»: the species' common name in Seriously Fish. Family: GBIF keeps it in Characidae and FishBase in Acestrorhamphidae; the profile follows GBIF.
Litres per fish and minimum tank height and depth: the profile's own judgement. Seriously Fish gives only the tank base and FishBase gives no tank sizes.
Lifespan: the profile's own estimate; the sources consulted do not give it.
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