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.

Tetras and Other Characins

Orange Von Rio Tetra

Glowlight Tetra

Red Eye Tetra

Black Skirt Tetra (Gymnocorymbus ternetzi)

Diamond Tetra

Head and Tail Light Tetra (Holopristis ocellifer)

Black Phantom Tetra (Megalamphodus megalopterus)

Lemon Tetra

Longfin Serpae Tetra

Rummynose Tetra

Black Neon Tetra (Hyphessobrycon herbertaxelrodi)

Cardinal Tetra (Paracheirodon axelrodi)