Costello Tetra Care Guide - Aquarium Setup, Diet & Breeding

The Costello Tetra is a small, lively characin with a slender, silvery body and a subtle golden to olive sheen. A dark lateral marking runs along the body, while the fins are generally transparent with delicate yellowish or reddish tones that become more noticeable when the fish is relaxed and settled in a group.

This peaceful tetra is an active midwater swimmer and is most impressive when several individuals move together through the aquarium. Although it is less brightly coloured than some popular tetras, its understated markings, alert behaviour and constant activity give a planted community aquarium plenty of character.

In the wild, Costello Tetras occur in the warm, slow-flowing waters of the Amazon region. These habitats may be shaded by overhanging vegetation and surrounded by submerged roots, fallen leaves and dense aquatic growth, creating a gently coloured and structurally complex environment.

Hemigrammus hyanuary is sometimes known as the January Tetra. It is a sociable species that tends to show its best behaviour and confidence when kept in a properly sized shoal, where the fish display natural exploratory and schooling movements.

Costello Tetras are native to the upper and central Amazon Basin in South America, particularly areas of Brazil and Peru. They inhabit slow-moving forest streams, tributaries and flooded habitats connected with the Amazon River system.

A group should be provided with at least a 60-litre aquarium, ideally measuring around 60 cm long by 30 cm wide or larger so there is adequate horizontal swimming space. Use a dark or natural substrate, gentle filtration and areas of dense planting alongside open water for schooling. Driftwood, roots, leaf litter and subdued lighting can recreate the shaded character of Amazonian streams, while a secure cover is useful because active tetras may jump.

Up to about 4.5 cm (1.8 inches) in total length. Females are usually slightly larger and deeper-bodied than males.

Costello Tetras are omnivores that accept a varied diet of quality small tropical flakes, micro-pellets and granules. Regular offerings of appropriately sized frozen or live foods such as baby brine shrimp, daphnia, cyclops and bloodworm help maintain condition and encourage natural feeding behaviour. Feed small portions that the group can finish quickly, with variety preferred over relying on one food alone.

Costello Tetras are peaceful community fish and can be kept with other similarly sized, non-aggressive species. Suitable companions include small rasboras, peaceful tetras, pencilfish, small Corydoras, otocinclus catfish, kuhli loaches and gentle dwarf cichlids. Avoid large predatory fish, fin-nippers and boisterous tankmates that may intimidate or consume them; they should also not be housed with aggressive cichlids or markedly larger species.

Costello Tetras are egg-scattering spawners that can be bred in a separate, dimly lit aquarium with soft, slightly acidic water and fine-leaved plants or a spawning mop. A conditioned pair or small group may scatter eggs among the vegetation, after which the adults should be removed because they may eat the eggs. The eggs usually hatch in about 24–36 hours, and the tiny fry can initially be offered infusoria or other suitably fine food before progressing to newly hatched brine shrimp.

Females are generally fuller through the belly, particularly when carrying eggs, while males are slimmer and may appear a little more streamlined. The differences are subtle, so sexing young or unconditioned fish can be difficult.