Purple Emperor Tetra
Inpaichthys kerri
Characidae
About
A small Brazilian characin from the Rio Aripuana in the upper Madeira basin, where it lives in sluggish, shaded forest tributaries stained brown and acidic by fallen leaves. Males glow violet-blue along the flank, carry a dark iridescent stripe from snout to tail and a blue adipose fin, while females are stockier, plainer and show a reddish adipose fin. Shops constantly sell it as an emperor tetra, but Nematobrycon palmeri is a different genus: larger, and with no adipose fin at all. Active but genuinely peaceful, it does best watching the tank from mid-water in a loose group.
Care
Keep at least eight in a 70 litre tank of 60 cm or more, with soft acidic water, driftwood, leaf litter and dim lighting. Any substrate suits this mid-water shoaler, though river sand shows off the biotope look and it also thrives in a well maintained, heavily planted tank. It dislikes alkaline water and is sensitive to nitrate creep, so change water regularly. The old fin-nipping reputation only surfaces when the group is too small; a proper shoal keeps the squabbling among themselves.
Diet
Flake and micro granules form the base, but supplement two or three times a week with live or frozen daphnia, cyclops and baby brine shrimp for colour and condition. Keep pieces small to suit the tiny mouth, and feed in modest amounts so nothing rots into the leaf litter.
Tankmate compatibility
Gets along with (75)
Possible with care (97)
Avoid (99)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Belly depthA hint only · only on well-fed adults, and only as a comparison
For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.
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Frequently asked questions
- What tank size does a Purple Emperor Tetra need?
- A Purple Emperor Tetra needs an aquarium of at least 70 litres (18.5 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Purple Emperor Tetra need?
- Purple Emperor Tetra does best at 22–28 °C (71.6–82.4 °F), pH 5.5–7.5 and a general hardness of 1–12 °dGH.
- What group size does a Purple Emperor Tetra need?
- Purple Emperor Tetra is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.
- Is the Purple Emperor Tetra suitable for beginners?
- Yes — Purple Emperor Tetra is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.