Cardinal Tetra

Cardinal Tetras (Paracheirodon axelrodi) are vibrant, peaceful, and schooling freshwater fish that make excellent additions to planted community aquariums. Here's a detailed care guide to help ensure your cardinal tetras thrive:

Aquarium Setup

• Tank Size: Minimum 38 litres, but a larger tank 75 litres or more is preferable for a larger school and more stable water conditions.
• Water Temperature: 23°C–27°C. They prefer warmer water, so use a reliable heater.
• pH Level: 4.5–8.0 (prefer slightly acidic water).
• Water Hardness: 1 to 4 dGH (very soft to moderately soft water).
• Filtration: Use a gentle filtration system, such as a sponge filter or low-flow hang-on-back filter. Cardinal tetras prefer calm water.
• Substrate: Soft sand or fine gravel works best. Cardinal tetras don’t interact much with the substrate, but they enjoy a natural setup.

Tank Mates

• Cardinal tetras are peaceful and should be kept with other non-aggressive, small species.
• Good Tank Mates: Neon tetras, guppies, rasboras, small catfish (like Corydoras), and peaceful dwarf cichlids like Apistogramma.
• Avoid: Aggressive fish or larger predatory species that may see the tetras as prey, such as large cichlids or fin-nippers like tiger barbs.
• Schooling: Always keep them in groups of at least 6–10, but a larger school (15+) will make them feel more secure and reduce stress.

Lighting

• Cardinal tetras are used to the shaded waters of South American rivers, so they prefer dim or moderate lighting.
• Floating plants like water lettuce or Amazon frogbit help diffuse light and create the ideal environment for them.
• Use a timer to ensure 8–12 hours of light per day to simulate their natural habitat and prevent stress.

Plants and Decorations

• Cardinal tetras thrive in a densely planted tank with plenty of hiding spots. Live plants like Java fern, Anubias, Amazon swords, Vallisneria, and cryptocorynes are excellent choices.
• Include driftwood and rock caves to mimic their natural habitat.
• Leave plenty of open swimming space in the center of the tank, as they are active swimmers and prefer mid-level water.

Water Quality and Maintenance

• Weekly Water Changes: Perform 20–30% water changes weekly to maintain water quality. Cardinals are sensitive to poor water conditions.
• Testing Parameters: Keep an eye on ammonia, nitrites, and nitrates. Cardinals are very sensitive to spikes in ammonia and nitrites.
• Water Stability: Stability is key—cardinal tetras don’t tolerate sudden changes in temperature, pH, or water hardness.

Feeding

• Cardinal tetras are omnivores and thrive on a varied diet:
  • High-quality flake food or micro-pellets.
  • Live or frozen foods: Bloodworms, brine shrimp, daphnia, or tubifex worms provide excellent nutrition and variety.
  • Vegetable matter: Occasionally provide spirulina-based foods or blanched veggies (e.g., zucchini) to offer a balanced diet.
• Feed small amounts twice a day, ensuring they consume everything within a few minutes. Uneaten food can pollute the tank.

Behavior and Health

• Schooling: Cardinal tetras are social, active, and happiest in a large school. They will display their brightest colors and natural behavior when kept in groups.
• Signs of Stress: Dull colors, hiding, or erratic swimming may indicate stress, poor water quality, or inappropriate tank mates.
• Disease Prevention: Be cautious of ich (white spot disease) and fin rot, both of which can affect tetras in poor conditions. Quarantine new fish and plants to prevent the introduction of diseases.

Breeding Cardinal Tetras

• Separate Breeding Tank: Breeding cardinal tetras in captivity is challenging, but possible. Use a separate breeding tank with soft, acidic water (pH 5.0–6.0) and low light.
• Temperature: Set the water temperature around 75°F–80°F (24°C–27°C).
• Spawning Conditions: Males and females should be conditioned with live or frozen foods before breeding. The female scatters eggs, and once eggs are laid, remove the parents as they may eat the eggs.
• Fry Care: The eggs hatch in 2–3 days, and fry can be fed infusoria or liquid fry food until they are large enough to eat baby brine shrimp.

Tips for Long-Term Success

• Acclimation: Cardinal tetras are very sensitive to water changes. Use a drip acclimation process when introducing them to a new tank to prevent shock.
• Tank Maturity: They do best in a well-established, cycled aquarium where water parameters are stable.
• Avoid Overcrowding: Overcrowding leads to stress and poor water quality. Stick to appropriate stocking levels.

By maintaining consistent water conditions, providing a peaceful environment, and feeding them a varied diet, your cardinal tetras will stay healthy, colorful, and active, bringing vibrancy to your aquarium.