Blue Tetra Care Guide - Aquarium Setup, Diet & Breeding

The Blue Tetra, Knodus borki, is a small, lively characin named for the vivid blue-green sheen that can flash across its flanks. In good condition, its body appears silvery beneath the colour, while the fins may show warm yellow, orange or reddish tones that add contrast to its blue colouring. The intensity of the display varies with mood, lighting and the fish's condition.

This is an active, peaceful shoaling fish that spends much of its time in the middle and upper areas of the aquarium. Blue Tetras are most impressive when kept in a proper group, where they form a constantly moving cluster and occasionally spar harmlessly with one another as they establish a social order.

In the wild, the species comes from tropical Amazonian waters shaped by seasonal rainfall and dense surrounding forest. Small characins such as this often use marginal vegetation, branches and leaf litter for cover, while open stretches of water provide room for quick feeding movements and escape from predators.

Although less commonly seen than some of the established commercial tetras, Blue Tetras have gained attention among aquarists looking for a colourful and unusual South American schooling fish. Their modest adult size and active nature make them a striking addition to a suitably arranged community aquarium.

Blue Tetras are native to the Rio Aripuanã basin in the Brazilian Amazon of South America. They inhabit clear to lightly tea-coloured rainforest streams and tributaries with submerged vegetation and structure along the margins.

A group of Blue Tetras should have at least a 60-litre aquarium, with a footprint of around 60 by 30 cm or larger. Use open swimming space alongside dense plants, fine branches, roots and areas of subdued cover, leaving gentle-flowing water for the shoal to explore. A dark fine-grained substrate, floating plants and leaf litter can help reproduce the shaded rainforest-stream atmosphere and bring out their colour. Keep the aquarium securely covered because active characins may jump.

Up to about 4.5 cm (1.8 inches) in total length. Females are generally a little deeper-bodied and may reach the larger end of this range, while males are usually slimmer and slightly smaller.

Blue Tetras are omnivorous micropredators. Offer a varied diet of high-quality small flakes or micro-pellets supplemented with frozen or live foods such as baby brine shrimp, daphnia, cyclops and finely chopped bloodworm. Small portions fed regularly help maintain their colour, activity and condition.

Blue Tetras are peaceful community fish and can be kept with similarly sized, non-aggressive species such as small Corydoras, peaceful rasboras, pencilfish, small peaceful barbs, other compatible tetras and gentle dwarf cichlids. Avoid large predatory fish, fin-nippers and boisterous tankmates that may intimidate them or view them as food. They should not be housed with aggressive cichlids or substantially larger species.

Blue Tetras are egg-scattering characins that can be bred in a separate, mature breeding aquarium. Use soft, slightly acidic water and fine-leaved plants or a spawning mop for the eggs. Condition a group with plenty of small live or frozen foods, then introduce the fish to the breeding tank. Spawning usually takes place among the vegetation, after which the adults should be removed because they may eat the eggs. The eggs hatch in roughly 24 to 36 hours, and the fry can be raised on infusoria or another suitably tiny first food before moving on to baby brine shrimp.

Females are typically fuller-bodied, particularly when carrying eggs, whereas males tend to be slimmer and more streamlined. Colour and fin shape can vary between individuals, so body shape is usually the most useful visible distinction.