Rainbow emperor tetra

Nematobrycon lacortei

Red eyes and irregular blue-green reflections above a dark band

The male has reddish-brown tones, iridescent scales and a dark band extending into the central tail.

Adult length: Up to 3.6 cm (standard length, without the tail fin)
Water temperature: 20–28 °C
pH: 5–7.2
Hardness: 1–10 dGH

Natural habitat: Native to the San Juan River basin in Colombia.

Males defend territories and may challenge similarly shaped fish. Provide broken sightlines and room to retreat.

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Appearance and identification

Compare the colour pattern with the emperor tetra, considering sex and lighting. Females tend to have blue-green eyes and shorter fins; eye colour alone is not enough for identification.

Same-species behaviour

Keep eight to ten or more of mixed sexes. Watch territorial interactions.

Space requirements

A 120 × 30 cm footprint, with wood and plants for shade. Small body length does not make this a small-tank fish.

Diet and feeding

Alternate small live or frozen foods with suitable dry foods.

Compatibility limits

Watch for chasing and suppressed tankmates; emperor-type tetras cannot all be treated as peaceful schoolers.

Aquarium environment

Use shaded planting and branches to interrupt sightlines. Numbers do not replace space.

Sources

www.fishbase.se ↗ 2026-10-25

www.seriouslyfish.com ↗ 2026-10-22

researcharchive.calacademy.org ↗ 2026-10-22

acshop.com.tw ↗ 2026-10-22

www.aquariumglaser.de ↗ 2026-10-22

repository.naturalis.nl ↗ 2026-10-22