The Cardinal Tetra (Paracheirodon axelrodi) is an iconic, vibrant freshwater fish native to the Orinoco and Negro River basins of South America. Famous for its brilliant, unbroken horizontal stripes of iridescent blue and striking cardinal red, it is one of the most popular schooling species in the aquarium hobby. While they resemble neon tetras, cardinal tetras grow slightly larger (up to 2 inches) and feature a red stripe that runs the entire length of their lower body. Quick Care Overview Parameter Target Range Tank Size Minimum 10 gallons (20 gallons preferred for large schools) Temperature 73°F – 81°F (23°C – 27°C) Water pH 5.5 – 7.0 (prefers soft, acidic water) Hardness 1 – 5 dGH Lifespan 2 – 5 years in captivity Natural Habitat & Setup Environment: In the wild, they inhabit shallow, slow-moving streams and flooded forest floors filled with leaf litter and fallen branches. Aquarium Decor: They thrive in heavily planted tanks with driftwood and dark substrate, which makes their colors pop. Water Quality: They are highly sensitive to sudden parameter shifts or poor water quality. Ensure your tank is fully cycled before introducing them. Add tannins using Indian Almond leaves to replicate their natural blackwater habitats. Behavior & Schooling School Size: Cardinal tetras are strict schooling fish and must be kept in groups of at least 6 to 10 individuals. Larger schools reduce their natural shyness and encourage active mid-water swimming. Tank Mates: Exceptionally peaceful community fish. Excellent companions include other small tetras, rasboras, Corydoras catfish, dwarf cichlids (like Apistogramma), and peaceful gouramis. Avoid large or aggressive tank mates that could easily view them as prey. Diet & Nutrition Feeding Habits: Omnivorous micropredators that constantly forage throughout the day. Aquarium Diet: They readily accept high-quality crushed flakes, micro pellets, and freeze-dried foods. For optimal coloration and health, supplement their diet with live or frozen treats like baby brine shrimp, Daphnia, and Moina.
