Blue/Purple Emperor Tetra (Inpaichthys kerri)

The Blue/Purple Emperor Tetra is often referred to as the “other” emperor tetra species—sharing many of the same elegant traits as its cousin (Nematobrycon palmeri), but generally hardier and more adaptable. Its striking appearance features a cream-toned body accented by a bold horizontal black stripe and subtle yellow edging on the fins. When mature, males in breeding condition display a gorgeous blue to purple sheen that makes this tetra a standout in any aquarium.

These fish are best kept in shoals of 6–10 or more. While males may display and compete for females, this behavior is harmless in a properly sized aquarium with plants and décor. Smaller groups, however, may become prone to fin-nipping of other tankmates.

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Behavior & Compatibility

The Blue/Purple Emperor Tetra is active and peaceful, spending most of its time in the top and middle levels of the tank, though it also ventures lower while feeding. It is safe with other peaceful, small species. Due to its relatively small mouth, it poses little threat to larger invertebrates, though it may prey on baby dwarf shrimp.

Being tank-raised, this species adapts well to aquariums, though it thrives best in soft, slightly acidic water enriched with tannins, leaf litter, or driftwood. It does not do well long-term in alkaline conditions (pH above 7.0).

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Diet & Feeding

While not fussy, the Blue/Purple Emperor Tetra thrives on a varied diet:

• Staple: High-quality flakes and small pellets

• Supplements: Frozen or freeze-dried foods like tubifex, daphnia, and bloodworms

• A protein-rich, diverse diet enhances both coloration and breeding behavior

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What We Love About This Fish

• Elegant blue/purple sheen in adult males

• Peaceful and community-friendly

• Hardy, adaptable, and active shoalers

• Excellent centerpiece or contrast fish for planted aquariums

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Recommended Tank Parameters

• Temperature: 76–80°F (24–27°C)

• pH: 5.5–7.0 (acidic preferred)

• KH: 4–8 dKH

• Minimum Tank Size: 20 gallons (school of 6+)

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Care Guidelines

• Diet: Omnivorous – flakes, pellets, frozen/live foods

• Social Behavior: Peaceful, shoaling; best in groups of 6+

• Origin: Tank-bred (native to South America)

• Adult Size: ~1.4 in (3.5 cm)

• Purchase Size: 0.75–1 in (1.9–2.5 cm)

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✨ Hardier than its cousin yet equally stunning, the Blue/Purple Emperor Tetra adds elegance, activity, and natural beauty to any peaceful community aquarium.