红吻半线脂鲤 · Rummy-nose tetra

Overview

Petitella rhodostoma is a rummy-nose tetra with a red head and a black-and-white tail. Two closely similar species are easily confused with it. Its gentle temperament and close schooling are best supported by a substantial group and consistently maintained water.

Distribution & habitat

It occurs in the Orinoco and lower Amazon basins of Venezuela and Brazil. Blackwater rivers and tributaries are typical habitats, with strongly acidic water tinted brown by substances released from decaying organic material.

Aquarium setup

Keep ten or more fish in an aquarium at least about 90 cm long. Sand, driftwood, roots, and leaf litter can provide a shaded, lightly tinted setting. Check and replace leaves regularly to avoid excessive decomposition. A carefully maintained planted aquarium is also suitable.

Weekly partial water changes are important. Poor conditions or alkaline water can cause fading, so head color should be considered alongside water quality and general condition rather than treated as a complete health or identification test.

Diet & feeding

This omnivore accepts a wide variety of appropriately sized foods. Its small mouth requires fine flakes or granules. Supplement prepared foods with small live and frozen items to maintain a varied diet and good color.

Behaviour & compatibility

Large or very boisterous companions can outcompete this peaceful tetra. Select gentle small fishes and suitable small catfishes. Maintain at least ten individuals, preferably more; inadequate numbers undermine both condition and natural schooling.

Sexual dimorphism

Mature females are distinctly rounder than males.

Breeding

Use a separate, very dim aquarium to raise larger numbers of fry. Fine plants, spawning mops, or mesh can protect the eggs. Soft, acidic water can be prepared with the help of reverse-osmosis water. Gentle sponge filtration is sufficient.

A group of approximately six fish of each sex can be used, or males and females can be conditioned separately before selecting a pair. This species spawns in the evening, an important difference from the familiar morning-spawning routine. Remove adults promptly when eggs appear because they will eat them.

Eggs hatch after about 24–36 hours, and fry become free-swimming three or four days later. Start with infusoria-sized foods before progressing to microworms and Artemia nauplii. Eggs and early fry are light-sensitive and should be kept as dark as possible.

Notes

Red does not extend onto the shoulder, but a dark spot is present on the lower rear caudal peduncle. The forward extension of the central tail band is narrower than in Petitella georgiae and more evident than in Petitella bleheri. Combine these features when identifying fish, since poor condition can obscure red coloration.

The fish most often sold as a rummy-nose tetra may belong to another species. Older literature uses Hemigrammus rhodostomus, and combinations retaining the epithet rhodostomus also occur, so searches may encounter different spellings.