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The Blue King Tetra, marketed under the name Boehlkea fredcochui / Knodus borki, is a small Amazonian characid valued for its silvery-blue coloration and active behavior. This schooling fish does best when kept in a group, in soft, clean and well-oxygenated water. Its slender body, blue reflections and constant swimming make it an excellent choice for a South American community aquarium. With an intermediate level of availability in the aquarium trade, it benefits from careful acclimation and a varied diet made up of small foods suited to its mouth.

General species description

Boehlkea fredcochui / Knodus borki is a small schooling fish belonging to the Characidae family. It mainly occupies the middle level of the aquarium and behaves more naturally when kept in groups of at least six, preferably more. Its activity is usually peaceful, although chasing among group members may occur during periods of excitement or spawning. It is suitable for a community aquarium containing small, calm fish. Efficient filtration, stable water conditions and regular water changes support its health. A rarity value of 2 indicates a species with moderate availability: it is known among aquarists but is not always offered by every retailer.

Geographic origin and biotope

Reference country: Peru. This species is associated with the upper Amazon basin, particularly the Rio Nanay region near Iquitos. It inhabits tropical streams with low to moderate flow, where the water is warm, soft and generally acidic to slightly acidic. The natural habitat includes wooded banks, submerged branches, leaf litter and areas shaded by riparian vegetation. In the aquarium, moderate lighting, roots and plants that create shelter reproduce its environment more effectively than a very open, brightly illuminated layout. Gentle to moderate circulation suits its swimming behavior and its need for well-oxygenated water.

Precise locality and local name

The main reference area is the Rio Nanay sector in northeastern Peru, near Iquitos, within the Amazon basin. In the aquarium trade, it is mainly sold as the Blue King Tetra, Blue Tetra or blue tetra. These trade names are more common than indigenous local names. The name Boehlkea fredcochui / Knodus borki has also been used in aquarium commerce and literature, which may explain why several scientific or trade names are associated with the same fish. To reduce identification errors, it is best to confirm the origin and characteristics of a particular shipment with the supplier.

Appearance and physical characteristics

The body is streamlined, laterally compressed and covered with small reflective scales. The base coloration ranges from silvery gray to steel blue, with stronger reflections when the fish is in good condition and kept in a stable group. The fins are translucent and may show a slight tint, while the lateral line remains subtle. Its slender shape and quick swimming are typical of a small midwater characid. Adult males are often slimmer, while females may have a rounder abdomen, especially when carrying eggs. Adult size generally remains close to 4 cm.

General diet

Boehlkea fredcochui / Knodus borki is omnivorous and readily accepts small commercial foods. A varied diet containing fine flakes, micro pellets, baby brine shrimp, cyclops and small frozen foods helps maintain its condition and coloration. Portions should be small so the group consumes them quickly, preventing food from accumulating on the bottom. Live or frozen foods can be offered regularly but should not replace a complete diet. Since the fish feeds mainly in the middle of the water column, distributing food in several areas helps reduce competition and allows more timid individuals to eat.

Essential data

• Name of the river of origin: Rio Nanay
• Local name used: Blue King Tetra; Blue Tetra
• Origin of the scientific name: Boehlkea fredcochui is the historical name; Knodus borki is the name currently associated with this species in several references.
• Etymology of the full name: Boehlkea is a genus name; fredcochui is a specific epithet. Knodus is a genus name; borki is a specific epithet.
• Common/vernacular names: Blue King Tetra, Blue Tetra, blue tetra
• Family: Characidae
• Subfamily: Characinae
• Name pronunciation: boehl-kay-ah fred-koh-koo-ee - noh-doos bor-kee
• Discovery: Jacques Géry, 1966
• Maximum adult size: about 4 cm
• Water temperature and pH: 24 to 28 °C; pH 5.5 to 7.0
• Stream appearance and surrounding vegetation: shaded tropical waterways, wooded banks, submerged branches and leaf litter
• Typical tankmates: small peaceful tetras, small corydoras, small loricariids, pencilfish, peaceful rasboras
• Temperament and behavior: peaceful, active and schooling; keep in a group
• Water depth: shallow to moderately deep areas
• Sexual dimorphism: males generally slimmer; females with a rounder abdomen
• Bottom structure and flow: sandy or detrital bottom, plant debris and low to moderate flow

In your aquarium

To succeed with Boehlkea fredcochui / Knodus borki, choose a mature, covered and well-filtered aquarium with open swimming space and shaded areas. Keep it in a group, avoid oversized or aggressive tankmates and provide fine foods several times each week. Stable, soft and slightly acidic water, along with gradual acclimation, are the most important factors. Regular water changes help preserve its coloration and natural behavior. This moderately available species rewards consistent care with a lively and attractive presence in the aquarium.