Blue Tetra – Knodus borki

Blue Tetra - Knodus borki

  • pH: 5.5-7
  • gH: 5-12
  • Temperature: 22-26C
  • Maximum Size: 5cm
  • Minimum Tank Size: 90 litres, 80x38x30cm


Knodus borki is a beautiful blue and silver tetra, native to Peru, sometimes sold as Cochu’s blue tetra. Although small, it is a very active fish which is why such a relatively large tank is necessary.


This is a peaceful but active, shoaling species which should be kept in a group of 6 or more to be seen at its best.  It can be nippy so shouldn’t be kept with slow-moving or longer finned tank mates, and its constant activity can be a problem for some species. Probably the best tankmates are those that occupy the bottom of the tank and that can cope with its boisterous behaviour, for example, small loricariids and corydoras. Other tetra species’ can be kept with the blue tetra too.

Housing and Feeding

A well-planted tank with floating plants for cover and to dim the light somewhat will show this fish at its best when its colours are truly stunning. In bare conditions, it can fade and look quite dull.

Feeding is straightforward as it is omnivorous and will eat pretty much anything offered including dry foods, though bloodworm, daphnia and frozen foods are appreciated.


Knodus borki is an egg scatterer, with the female choosing a spot beneath the leaves of plants to lay her eggs. When the fry hatch they are extremely small and once their yolk sacs have been absorbed they will feed on infusoria initially as they are too small to take larger foods. Successful breeding in a community aquarium is unlikely as both the parents and tank mates will eat both eggs and fry.


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