Tetra Cosmic Blue: A Stunning Gem for Your Aquarium

Characteristics

The Tetra Cosmic Blue is a mesmerizing freshwater fish from the Characidae family, admired for its iridescent blue hues. As a small, peaceful schooling fish, it makes a fantastic addition to community aquariums. This species thrives in the following conditions:

• Water Temperature: 22–27°C (72–81°F)
• pH Level: 5.5–7.0
• Water Hardness: Soft to moderately hard (2–10 dGH)
• Tank Size: Minimum 10 gallons (for small schools)
• Behavior: Peaceful, active swimmer
• Care Level: Easy

Origin and Distribution

The Cosmic Blue Tetra originates from South America, particularly in slow-moving rivers, floodplains, and forest streams in the Amazon basin. These habitats are rich in tannins from decayed leaves and wood, creating slightly acidic water conditions.

Colors and Markings

As its name suggests, the Cosmic Blue Tetra displays a dazzling metallic blue body that shimmers under aquarium lighting. It may also have hints of violet or silver depending on the angle of light. This iridescence makes it a true centerpiece in any tank. Its fins are mostly translucent, with a slight bluish or silver tint.

Tankmates

Being a peaceful schooling fish, the Cosmic Blue Tetra thrives best when kept in groups of at least 6–8 individuals. Suitable tankmates include:

✅ Other Tetras (Neon, Cardinal, Rummy Nose, Glowlight)
✅ Rasboras
✅ Corydoras Catfish
✅ Dwarf Gouramis
✅ Otocinclus Catfish
✅ Dwarf Shrimp (such as Cherry or Amano Shrimp)

🚫 Avoid keeping them with large, aggressive species like Oscars or aggressive fin-nippers such as Tiger Barbs.

Care Requirements

To keep Cosmic Blue Tetras healthy and vibrant, ensure:

• Stable water parameters with regular weekly water changes (20%).
• A well-planted aquarium with driftwood or leaf litter for a natural setup.
• Dim to moderate lighting to enhance their blue iridescence.
• A gentle filtration system to mimic their natural slow-moving habitat.

Diet and Feeding

Cosmic Blue Tetras are omnivorous and enjoy a variety of foods:

• High-quality micro-pellets or flakes
• Live or frozen foods (daphnia, bloodworms, brine shrimp)
• Vegetable-based foods (spirulina flakes, blanched zucchini)

Feed them small portions twice daily to maintain their health and coloration.

Gender Differences

Males typically have brighter blue coloration and a slimmer body, whereas females are slightly rounder, especially when carrying eggs. Males may also display increased coloration during breeding attempts.

Breeding

Breeding Cosmic Blue Tetras in captivity is possible with proper conditions:

• A separate breeding tank with soft, acidic water (pH 5.5–6.5).
• Fine-leaved plants or a spawning mop for egg-laying.
• Dim lighting, as bright light may discourage spawning.

Females scatter eggs among plants, and the eggs hatch in 24–36 hours. The fry should be fed infusoria or powdered fry food until they are large enough for regular food.

Additional Resources

For more aquarium care tips, check out:

• Top 10 Tetras for Community Tanks
• Best Tank Setup for Colorful Tetras
• How to Maintain a Planted Aquarium for Small Fish