Ruby Tetra (Axelrodia riesei)

Axelrodia riesei comes out of Colombian blackwater, tiny even by nano-tetra standards, and carries a deep ruby-red saturation that's easy to mistake for a dyed fish until you learn it's simply how the species colors up under soft, tannin-stained water. It shares a namesake with the cardinal tetra, both honoring Herbert Axelrod, a major figure in popularizing South American blackwater species in the aquarium trade. Best in a real group in a calm, densely planted nano tank rather than a busy community setup.

Care level: Moderate · Temperament: Peaceful, shoaling · Max size: ~0.75" · Min tank: 10 gal · Diet: Omnivore, micro-pellet/flake