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Maximum size : 4 cm

Blue Purple Emperor Tetra - Inpaichthys kerri : Complete Fish Profile & Care Guide

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The Purple Emperor Tetra (Inpaichthys kerri) is an active and peaceful species that forms shoals in the wild. Although they have been erroneously associated with fin-nipping, such behaviour can be mitigated by keeping them in sufficiently large groups of ten or more individuals and providing enough visual barriers within the aquarium. This will promote a sense of security among the fish, reduce aggression between males and create a natural-looking display, with males displaying their best colours when competing for females.

When selecting tankmates for the Blue Emperor Tetras, it is essential to choose small and peaceful species, such as Corydoras Catfish, Pencilfish, and small Dwarf Cichlids, including Mikrogeophagus or Apistogramma. Rasboras, smaller Gouramis, and peaceful Barbs are also good options. It is crucial to maintain good water quality, as Blue Emperor Tetras are sensitive to high nitrate levels and water chemistry fluctuations. A well-decorated aquarium with driftwood, moderate planting, and subdued lighting will simulate their natural habitat and make them feel more secure.

Male and female Blue Emperor Tetras display differences in colouration. The male's body is entirely light purplish-blue except for its beige stomach, with a thick iridescent dark blue stripe that extends from the snout through the eye and caudal fin. The male's dorsal fin is elongated, and the adipose fin is blue, while their other fins are transparent, except for the pectoral and anal fins, which have a hint of blue. In contrast, females have an elongated dorsal fin and a reddish orangy-brown adipose fin. They possess a thick black line above them, with beige areas and a silvery-blue sheen. The belly is white, occasionally with a silvery sheen, and its fins are transparent.

Blue Purple Emperor Tetra Photos

Sexual Dimorphism

Differentiating between male and female Purple Emperor Tetras is a simple task. Male specimens typically exhibit a more vibrant colouration and are slimmer in build. They also grow larger and possess a rounded anal fin. Conversely, females have a stockier body shape, lack the brightness of their male counterparts, and have an angular anal fin.

Quick Facts

Scientific NameInpaichthys kerri
Year Described1977
Other NamesRoyal Tetra, Blue Kerri Tetra, Blue Purple Emperor Tetra, Regal Teta
Max Size4 cm
Aquarium LevelMiddle - Top
Best kept asGroups 10+
LifespanUp to 6 Years

Water Parameters

Water TypeFreshwater
PH6.0 - 7.5
GH3 - 12
73 - 79
22 - 26

Natural Habitat

The Purple Emperor Tetra is a truly exotic species originating from the pristine waters of the Aripuana River. This river forms a vital part of the upper Madeira River Basin, nestled in the heart of Mato Grosso in northwestern Brazil. In the wild, these strikingly beautiful fish prefer to inhabit the calm and acidic waters of the slow-moving tributaries. The waters in these regions are crystal clear, but the brownish hue of the water indicates the presence of tannins released by the decaying leaves that fall from the lush forest canopy above.

 Madeira River - Brazil
Brazil Flag


Purple Emperor Tetras are known to be prolific breeders in captivity. If you are interested in raising a sizable number of fry, a separate breeding tank should be set up. The breeding tank should be dimly lit and feature bundles of fine-leaved plants such as java moss or spawning mops where the fish can deposit their eggs. Alternatively, the tank's bottom can be covered with mesh with appropriately sized holes to allow the eggs to fall through but keep the adults from reaching them. The water in the breeding tank should be soft and acidic, and the temperature needs to be slightly higher than in their regular aquarium. A small air-powered sponge filter is sufficient for filtration.

Spawning can occur in a group, with six individuals of each sex being ideal. However, conditioning with plenty of small live and frozen foods is crucial before spawning to prevent complications. Alternatively, spawning can occur in pairs. In this case, the fish should be conditioned separately in male and female groups before choosing the fattest female and best-coloured male for breeding. The adults will eat the eggs if given a chance, so it's vital to remove them from the tank as soon as possible.

The eggs usually hatch within 24-48 hours, and the fry becomes free-swimming within 3 to 4 days. The fry can be fed with infusoria-type foods for several days until they are large enough to accept microworm or baby brine shrimp.

Diet & feeding

Purple Emperor Tetras are not a finicky species when it comes to their dietary preferences. They have no special requirements and will readily consume most commercial dried foods like flakes, granules and pellets. However, to promote optimal health and colouration, it is essential to supplement their diet with small live and frozen fares such as bloodworm, white mosquito larvae, daphnia and brine shrimp. A varied and balanced diet will not only ensure your fish thrive but also support their growth and development.

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