彩虹丝尾脂鲤 · Rainbow Tetra

Overview

Nematobrycon lacortei, the rainbow tetra, is a vividly colored fish from western Colombia. Males use their elongated fins during displays. Although generally suitable for a peaceful community, adult males defend space and compete for rank, so its small size should not lead to cramped housing.

Distribution & habitat

The species is considered endemic to the San Juan drainage in western Colombia. Available records appear to concern the Calima, a tributary in the lower basin. It apparently occupies isolated forest pools in the Calima headwaters, possibly upstream of the dam; the precise distribution remains uncertain.

Aquarium setup

Use an aquarium at least about 120 × 30 × 30 cm. Decoration is flexible, but live plants and ample cover encourage stronger colors. Soft sand with roots and branches can create several shaded areas. Dried leaves add shelter and develop microbial growth that offers supplementary food for fry.

Diet & feeding

The natural diet is probably opportunistically omnivorous. Captive fish are usually easy to feed. Combine quality flakes or granules with small live or frozen foods such as Daphnia, Artemia, and bloodworms.

Behaviour & compatibility

Maintain a mixed-sex group of at least 8–10 fish. Other peaceful schooling species can help provide security. Males display strongly when competing for females or rank, and their territorial aggression can extend to fishes with a similar shape. Select companions of comparable size without predatory tendencies, and provide sufficient room and visual barriers.

Sexual dimorphism

Adult males have red eyes, stronger colors, and more elongated dorsal, anal, and caudal fins. Females have blue-green eyes and fuller bodies, particularly when carrying eggs.

Breeding

Breeding is reported to follow the general method used for its congener. Prepare a dim aquarium with fine plants, spawning mops, or protective mesh. Soft, acidic water around pH 5.0–7.0, 1–8 degrees GH, and 24–26.5 °C can be used, together with gentle sponge filtration.

Condition males and females separately before moving a visibly gravid female and a male into the breeding aquarium in the evening. Spawning often starts the next morning, with small batches of eggs deposited over several hours. If no eggs appear after a few days, try another pair. Remove the adults after spawning to prevent egg predation.

Hatching usually takes 24–36 hours, followed by free swimming four or five days later. Feed infusoria-sized foods for approximately the first week, then introduce microworms or Artemia nauplii as the fry can handle them.

Notes

Its close relative Nematobrycon palmeri is similar in form but has a distinct color pattern. Threadlike tail extensions alone do not distinguish the two.