帝王灯 · Emperor Tetra

Overview

Nematobrycon palmeri, the emperor tetra, is an active, colorful schooling fish with a generally peaceful disposition. Most specimens sold are commercially bred and adapt readily to aquarium foods and water conditions. Territorial interactions between males still make space and cover necessary.

Distribution & habitat

Its native range is restricted to Colombia's San Juan and Atrato basins. It occurs widely in slower river reaches, minor tributaries, and backwaters. Wild-caught specimens are now less prominent in the trade than farmed fish.

Aquarium setup

Provide a footprint of at least about 90 × 30 cm. Ample decoration breaks up encounters between competing males. Increase the available space when keeping a larger group.

Diet & feeding

In nature it probably hunts small insects, worms, crustaceans, and other zooplankton. Appropriately sized dry foods are accepted, but should not make up the entire menu. Daily additions of small live or frozen foods such as Daphnia and Artemia encourage good color and breeding condition.

Behaviour & compatibility

Peaceful tetras, rasboras, danionins, small catfishes, and suitable dwarf cichlids can be companions. Avoid fishes large enough to swallow it. Keep at least six emperor tetras, preferably ten or more. Rival males defend space, but serious injury is uncommon when the aquarium is sufficiently large and well furnished.

Sexual dimorphism

Males grow larger and more colorful, developing elongated dorsal, anal, and caudal fins. The central tail ray becomes particularly extended. The iris is blue in males and green in females.

Breeding

Breeding is relatively straightforward. To raise substantial numbers, prepare a dim aquarium with fine plants, spawning mops, or mesh to protect the eggs. Soft, acidic water around pH 6.0–7.0, 1–10 degrees GH, and 24–26.5 °C, with gentle sponge filtration, is suitable.

A group of approximately six fish of each sex can spawn, but needs extra space for male territories. Pair breeding is generally more productive. Condition the sexes separately, then transfer a gravid female and a well-conditioned male in the evening. Small batches of eggs are usually laid the following morning over several hours. Try a different pair if nothing happens after a few days.

Adults eat their eggs, so removing them after spawning is the more reliable approach. In an exceptionally dense planted aquarium, another option is to leave adults in place and siphon out fry as they appear. Eggs hatch after about 24–36 hours; free swimming follows four or five days later. Supply infusoria-sized food for roughly the first week, then graduate to microworms and Artemia nauplii.

Notes

The male's blue iris distinguishes it from the red-eyed male rainbow tetra, Nematobrycon lacortei. Another frequent source of confusion is Inpaichthys kerri, which is smaller, lacks comparable fin extensions, and has an adipose fin. Emperor tetras lack that fin. The so-called black emperor is generally treated as a dark color form of this species.