Cardinal tetras (Paracheirodon axelrodi) are among the most prized fish in the freshwater hobby, famous for their vivid red and neon blue stripes. Unlike their close cousins the neon tetra, cardinals are primarily wild-caught, making captive breeding a significant challenge and a worthy goal.

To breed cardinal tetras, you'll need a dedicated breeding tank: a small, 10-20 gallon aquarium with very soft, acidic water (pH 5.5-6.5, TDS under 50 ppm). A reverse osmosis filter is almost essential to achieve these parameters. Temperature should be around 26-28°C (79-82°F).

Lighting must be very dim — use floating plants or cover part of the tank. Cardinals spawn in darkness, so a blackout period is often used. Add java moss or fine-leaf plants for spawning sites.

Conditioning the parents: Feed the breeding pair live or frozen foods (daphnia, micro worms, baby brine shrimp) for 2-3 weeks before attempting to spawn.

Spawning behavior: The male will chase the female in the evening. Eggs are scattered among the plants and are light-sensitive — after spawning, cover the tank completely. Eggs hatch in 24 hours, and fry become free-swimming around day 5. First foods: infusoria, then newly hatched brine shrimp.