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Cardinal tetra

Paracheirodon axelrodi

Photo: Cardinal tetra
Weights and measures
Length 4,5 cm
Animal description
The Cardinal Tetra (Paracheirodon axelrodi) is a small, vibrant freshwater fish native to the upper Orinoco and Negro rivers in South America. This species is a member of the Characidae family, which encompasses many other tetra species. Its stunning appearance and peaceful nature make it a favorite among aquarium enthusiasts worldwide.

Characterized by its iridescent blue line that runs horizontally along its body, from the tip of its nose to the base of its adipose fin, the Cardinal Tetra is a sight to behold. Beneath this shimmering blue stripe lies a contrasting deep, rich red that covers the lower half of the body, extending from the middle of the body to the caudal fin. This vivid coloration not only serves as an attractive feature in home aquariums but also plays a role in the fish's natural habitat, helping it to camouflage among the dark waters and dense vegetation.

Adult Cardinal Tetras typically reach a size of about 2 inches (5 cm) in length. They possess a slender, somewhat compressed body shape, which is ideal for navigating the complex environments of their native river systems. Their fins are relatively small and transparent, with the exception of the adipose fin, which is a small, fleshy fin located between the dorsal and caudal fins.

In the wild, Cardinal Tetras inhabit slow-moving, acidic waters that are heavily tinted with tannins from decaying vegetation, often referred to as "blackwater" environments. These conditions contribute to the low pH levels and soft water that the species thrives in. They are schooling fish that prefer to live in large groups, a behavior that provides safety in numbers from predators. Their diet primarily consists of small invertebrates, plant matter, and plankton.

Breeding Cardinal Tetras in captivity can be challenging due to their specific water condition requirements. They are egg scatterers, meaning they do not exhibit parental care. Instead, after spawning, the adults must be removed to prevent them from consuming their eggs. The fry are extremely small and require infusoria or similarly sized food until they are large enough to eat standard aquarium fare.

The Cardinal Tetra's remarkable beauty, coupled with its peaceful demeanor, makes it a popular choice for community aquariums. However, their care requires attention to detail, particularly in maintaining the water quality and conditions that mimic their natural habitat. They are best kept with other small, peaceful fish species and thrive in well-planted aquariums that offer plenty of hiding spots.

As a testament to their popularity, Cardinal Tetras are heavily collected for the aquarium trade, which has raised concerns about the sustainability of wild populations. However, significant efforts have been made to establish captive breeding programs to reduce the pressure on natural stocks.

In summary, the Cardinal Tetra (Paracheirodon axelrodi) is a captivating freshwater fish that enchants aquarists with its vivid colors and serene nature. Its care requires a commitment to replicating the soft, acidic water conditions of its native habitat, but for many, the beauty of this fish makes the effort well worth it.
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