Cardinal tetra

The cardinal tetra reaches about 3.5 cm standard length and is widely considered the showier cousin of the neon tetra — the red band runs the full length of the body rather than halfway. It inhabits blackwater streams of the Rio Negro basin in Brazil and parts of the Orinoco watershed, where the water is soft, acidic, and stained brown by humic substances. A tank with a base of 60 by 30 cm (about 54 L) can house a school of ten or more fish, and they are best kept in such numbers to bring out natural behaviour. Temperature of 23–29 °C and pH ranging from 3.5 to 7.5 covers both wild and captive-bred stock, though wild specimens prefer more acidic conditions. Heavily planted setups with subdued lighting, floating vegetation, and dark substrate show the iridescent blue stripe to best effect. Diet is omnivorous — fine flake, micro pellets, and small live or frozen foods. They are generally peaceful and mix well with other small characins, rasboras, and dwarf cichlids. Commercially bred strains (gold, albino) are available but wild-caught fish remain a significant part of the trade and support community-based projects along the Rio Negro.