Cardinal Tetra

About

The cardinal tetra (Paracheirodon axelrodi) is probably the most recognizable freshwater fish in the hobby after its close relative the neon tetra, and for good reason. Where the neon's red band covers only the rear half of the body, the cardinal's vivid red runs the full length of the belly, paired with a broad iridescent blue-green lateral stripe that seems to glow under aquarium lighting. Wild fish come from the soft, acidic blackwater tributaries of the upper Orinoco and Negro river basins in South America, where they gather in large shoals in the middle water column. Interestingly, that famous blue stripe may function as a predator-confusion device in their dark native waters, projecting mirror images onto the water's surface from certain angles. A significant portion of the fish sold today are still wild-caught, and sustainable community harvest projects in the Barcelos region of Brazil depend heavily on this species for local income. In the aquarium, cardinals are gentle, peaceful fish that do best in groups of eight or more, ideally alongside similarly sized, non-aggressive tankmates. They're not difficult to keep once settled, but they are sensitive to water quality and abrupt parameter shifts, so they suit a keeper with some experience running a stable, established tank. Breeding is possible but genuinely challenging.