Cardinal Tetra

Overview

The Cardinal Tetra (Paracheirodon axelrodi) is one of the most iconic freshwater aquarium fish, prized for its vivid iridescent blue lateral stripe paired with a deep red lower body that extends the full body length — distinguishing it from the similar Neon Tetra. Native to the blackwater streams of the Amazon and Orinoco basins, it thrives in soft, acidic water.

Water Parameters

• Temperature: 24–28°C (75–82°F); tolerates 22°C but colours best above 25°C
• pH: 4.5–6.5 (prefers below 6.0; hard water will fade colour and shorten lifespan)
• Hardness: 1–4 dGH (very soft water ideal)
• Ammonia/Nitrite: 0 ppm; sensitive to spikes during cycling

Tank Setup

• Minimum tank size: 55 litres for a group of 10+
• Substrate: Dark sand or fine gravel enhances colour
• Decor: Dense planting with driftwood, leaf litter (Indian Almond leaves, oak leaves), and floating plants to dim light and release tannins
• Flow: Gentle; they come from slow-moving streams
• Cover: Tight-fitting lid recommended; they are not jumpers but can dart when startled

Diet

• Base: High-quality micro flake or granule (e.g., crushed flake, Sera Micron)
• Treats: Frozen daphnia, baby brine shrimp, microworms
• Frequency: 2 small meals daily; they are constant grazers
• Note: A varied diet maintains vibrant colour — avoid relying solely on dry food

Temperament & Tank Mates

• Temperament: Peaceful, shy, schooling — never keep fewer than 8
• Best companions: Corydoras, small rasboras, dwarf shrimp (adults), Otocinclus, dwarf gouramis
• Avoid: Large or boisterous fish (cichlids, barbs, tiger barbs); even medium fish may view them as food
• Schooling: Tight schooling fish — groups of 15+ create stunning visual displays

Breeding

• Difficulty: Moderate; requires very soft, acidic water (pH below 5.5)
• Process: Scatter eggs among fine-leaved plants; remove parents as they eat eggs
• Fry diet: Infusoria, micro worms, powdered flake

Common Issues

• Fading colour often indicates hard or alkaline water
• Sensitive to sudden parameter changes — acclimate slowly (drip method recommended)
• Prone to "neon tetra disease" (Pleistophora hyphessobryconis) — no cure; quarantine new fish
• Lifespan: 2–3 years in ideal conditions