Ruby tetra

Axelrodia riesei

A tiny red tetra with a dark tail-base patch

Look for the dark patch at the tail base as well as the red colour. A mature, soft, acidic aquarium and fine food matter more than its small size suggests.

Adult length: Up to 2 cm (standard length, without the tail fin)
Water temperature: 20–28 °C
pH: 4–6.5
Hardness: 1–5 dGH

Natural habitat: Native to the upper Meta River basin.

Sensitive to immature conditions and accumulating organic waste. Its small mouth requires fine food.

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Appearance and identification

Compare the tail-base patch with the ember tetra rather than relying on red colour alone. Ruby colour varies between individuals and conditions; stronger red trade labels are not separate species. Adult males tend to be slightly smaller and more intensely coloured; mature females are rounder, especially when carrying eggs.