09/28/2026
The Cardinal Tetra, Paracheirodon axelrodi, is more than just a brighter Neon Tetra its natural range is centred on the Rio Negro and upper Orinoco, where populations can differ subtly in colour and morphology. In the Negro, it lives in acidic, extremely soft forest streams stained by leaf litter and humic compounds, forming large seasonal schools as water levels change. Despite being one of the most familiar tetras in the hobby, successful captive breeding still requires very soft, acidic water and darkness because the eggs and early fry are highly light sensitive. Wild fish remain an important part of the trade, including fish entering through community based fisheries around the Rio Negro.