1 kinds · tap one for a closer look
Peaceful.
259 species in our list are a good match.
Peaceful.
Flakes and small foods.
Tap a food to see what it is.
Males are more colourful and slimmer; females are stockier and much duller, and have a mainly red adipose fin (blue in males).
Common problems. Tap one to see the signs. This is a guide, not a diagnosis.
Egg-scatterer · Moderate
Egg scatterer that has been spawned regularly in the hobby, in dim tanks with fine-leaved plants or mesh; adults eat the eggs and should be removed.
Keep a group of 8-10 and move a well-conditioned trio or group to a spawning tank.
30-40 L tank with a spawning grid or dense java moss, soft to medium water (pH 6-7.5), a sponge filter and subdued light.
Heavy live-food conditioning, then a water change with slightly cooler water in the morning.
No egg count found. Eggs hatch in 24-48 hours and the fry swim free 3-4 days later; first foods are infusoria, then microworm or brine shrimp nauplii.
Start with infusoria or powdered fry food, then newly hatched brine shrimp; sort by size as they grow.
A small blue-purple tetra from the Rio Aripuanã and upper Madeira basins of Brazil, sold as royal, regal, blue emperor or purple emperor tetra; it lives in slow, tannin-stained forest streams.
Jacques Géry and Wolfgang Junk described the royal tetra in 1977, naming both genus and species after Brazil's INPA research institute and its director. It comes from a fairly small area in the southern Amazon. Its blue-violet colours made it a popular aquarium fish, and it is now widely bred.
First described by Jacques Géry & Wolfgang Junk in 1977. Named for Genus named after INPA (Brazil's national Amazon research institute); species honours its director Warwick Kerr.
16 facts checked with sources
Valid. The genus is no longer monotypic: I. parauapiranga (2024, same Aripuanã drainage), I. nambiquara (moved from Hasemania, 2024) and I. luizae (2025) were added, so wild imports could include look-alikes. Also sold as purple emperor, blue emperor or regal tetra and confused with the emperor tetra (Nematobrycon palmeri), which lacks an adipose fin.
Eschmeyer's Catalog of Fishes: species in Inpaichthys (updated 21 Sep 2026) · FishBase: Inpaichthys kerri summaryLegacy has no family. Moved from Characidae to Acestrorhamphidae in the 2024 split of Characidae (Melo et al. 2024).
FishBase: Inpaichthys kerri summary · Eschmeyer's Catalog of Fishes: species in Inpaichthys (updated 21 Sep 2026)Size rule: larger figure used, Seriously Fish 3.5 cm SL (standard length) vs FishBase 2.8 cm SL. Legacy 4 cm is close to total length.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra) · FishBase: Inpaichthys kerri summaryBoth sources 24-27 °C; legacy 23-28 °C slightly wide.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra) · FishBase: Inpaichthys kerri summarySeriously Fish used for husbandry; FishBase gives 6.0-8.0. Legacy 5.5-7.5.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra) · FishBase: Inpaichthys kerri summaryLegacy has no hardness.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra) · FishBase: Inpaichthys kerri summary60 x 38 x 30 cm = 68.4 L. Legacy 40 L is too small.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra) · FishBase: Inpaichthys kerri summaryMay nip fins if kept in too small a group (Seriously Fish).
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra)Legacy 'middle' not confirmed.
FishBase: Inpaichthys kerri summaryLegacy has no range field (story says Brazil).
Eschmeyer's Catalog of Fishes: species in Inpaichthys (updated 21 Sep 2026) · FishBase: Inpaichthys kerri summaryMatches legacy; the adipose-fin colour is an extra, reliable cue.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra)Legacy 'egg scatterer, easy' confirmed. Spawning water pH 5.5-6.5, gH 1-5, 24-28 °C (Seriously Fish).
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra)Legacy '100-300 eggs' not confirmed.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra)Legacy 'deep-blue tetra from Brazil' fits; its 'yellow-gold front half' was not found in sources, so it is left out.
Seriously Fish: Inpaichthys kerri (Purple Emperor Tetra)