Cardinal Tetra

The Cardinal Tetra is one of the most iconic and beloved aquarium fish in the hobby, often confused with its cousin the Neon Tetra but distinguished by its vibrant red coloration that extends the full length of its body. Native to the blackwater tributaries of the Amazon Basin in Brazil and Colombia, these stunning fish display brilliant blue and red horizontal stripes that seem to glow under proper lighting. Unlike Neon Tetras, the Cardinal Tetra's red stripe runs from head to tail, making them slightly more striking. They are active swimmers that thrive in schools of six or more, creating a mesmerizing display of color as they move together through the water. Their peaceful nature and moderate care requirements make them excellent choices for community aquariums, though they do require stable water conditions and soft, acidic water to display their best colors and maintain long-term health.

Care Requirements

Tank Setup

Cardinal Tetras require a well-planted aquarium with plenty of hiding spots and swimming space. Use driftwood, rocks, and dense vegetation like Amazon swords, java moss, and cryptocoryne to create a natural Amazonian biotope. Dim lighting enhances their colors and reduces stress. Dark substrate helps their colors pop. A gentle filter current mimics their natural slow-moving water habitat.

Water Quality

• Temperature: 73-81°F (23-27°C)
• pH: 5.5-7.0
• Water Hardness: Soft (1-5 dGH)
• Ammonia/Nitrite: 0 ppm
• Nitrate: <20 ppm

Cardinal Tetras are sensitive to water parameter fluctuations and poor water quality. Regular water changes (25-30% weekly) are essential to maintain pristine conditions.

Feeding

Cardinal Tetras are omnivores with small mouths. Feed small portions 2-3 times daily:

• High-quality micro pellets or crushed flake food as staple
• Frozen or live foods: baby brine shrimp, daphnia, microworms
• Occasional vegetable matter: blanched spinach or spirulina

Avoid overfeeding as they have small stomachs and uneaten food quickly degrades water quality.

Behavior & Compatibility

These peaceful schooling fish must be kept in groups of 6-10 minimum, ideally 15-20+ for the best display. They establish a pecking order within the school and feel secure when in large numbers. They occupy the middle to upper water column and rarely bother other tank inhabitants. Their gentle nature makes them excellent dither fish for shy species like Apistogramma and discus.

Common Health Issues

1. Neon Tetra Disease (Pleistophora hyphessobryconis): Causes color loss, swimming difficulties, and spinal deformities. Highly contagious and often fatal; quarantine new fish and remove affected individuals immediately.
2. Ich (White Spot Disease): Appears as white spots on fins and body. Treat with increased temperature and medication.
3. Stress-related illness: Poor water conditions cause faded colors, lethargy, and increased susceptibility to disease.

Breeding

Breeding Cardinal Tetras in captivity is challenging but possible. They require very soft (1-2 dGH), acidic water (pH 5.0-5.5) and dim lighting. Spawning typically occurs on fine-leaved plants or a spawning mop. Parents should be removed after spawning as they will eat eggs. Eggs hatch in 24-36 hours, and fry require infusoria and newly hatched brine shrimp.

Tips for Success

• Always buy from reputable sources; wild-caught specimens may carry parasites
• Acclimate slowly using drip method over 45-60 minutes
• Keep in larger schools (15+) for best coloration and confidence
• Use tannins from driftwood or Indian almond leaves to soften water
• Test water parameters weekly to catch issues early
• Quarantine new additions for 2-3 weeks before adding to main tank