Knodus borki · Blue Tetra

Overview

The intense blue of Knodus borki is natural rather than artificial coloring. This vigorous swimmer may nip fins, particularly during feeding or in cramped quarters. Space, a sufficient group, and generous cover matter, and it is unsuitable as a reassuring companion for timid dwarf cichlids.

Distribution & habitat

It occurs in Colombia and Brazil, inhabiting rivers, streams, and tributaries.

Aquarium setup

Small size should not obscure its need for swimming room. Dense planting, dark substrate, and floating cover bring out the best color; sparse surroundings often produce a disappointing display.

An alternative uses sand, beech branches and roots, and dried oak, beech, or Indian almond leaves. Aquarium-safe peat in the filter can help stain the water. Maintain plenty of dissolved oxygen. Alkaline conditions are unsuitable.

Diet & feeding

An omnivore accepting a broad range of foods, it particularly enjoys small live or frozen bloodworms, water fleas, and brine shrimp. Include plant material such as blanched spinach or good Spirulina flakes.

Behaviour & compatibility

Generally compatible with suitable companions, it can nevertheless nip conspecifics and long-finned fishes. Feeding excitement and confinement make this more noticeable. Eight to ten or more in a larger aquarium usually reduce the problem and keep most rivalry within the group.

Avoid very quiet or slow-moving companions, which may be intimidated by its constant activity. It is not an appropriate dither fish for shy dwarf cichlids. Robust tetras and suitable small suckermouth or cory catfishes are possible alternatives after checking size and water requirements.

Sexual dimorphism

Mature females have a clearly rounder abdomen, while males show slightly stronger color. A reddish anal fin is reported in spawning males but should not be treated as an absolute sexing rule.

Breeding

Captive reproduction has been achieved, although details are limited. Use a separate bare-bottomed aquarium with a small air-driven sponge filter and broad-leaved plants. Egg deposition beneath a leaf is reported rather than firmly established, but providing such surfaces is reasonable.

Prepare mature, acidic soft water within the species' appropriate hardness range. Condition the group with high-quality live and frozen foods. Once females are plump and males strongly colored, move a selected pair in the evening.

Remove the adults if eggs are found the next morning because they may eat them. The very small fry require Paramecium or comparable microscopic live foods initially.

Notes

Suitable surroundings allow its natural blue to develop fully. Weak coloration in a bare display should not be interpreted automatically as a different identity or fading artificial dye.