Celestial Pearl Danio

The Celestial Pearl Danio, also known as the Galaxy Rasbora or CPD, is a stunning nano fish discovered in Myanmar in 2006. These tiny fish (under 1 inch) quickly became one of the most popular nano aquarium fish due to their spectacular coloration - dark bodies covered in iridescent blue-green spots with bright orange-red fins. They are peaceful, schooling fish perfect for small planted tanks. Despite their small size, they have big personalities and active behaviors. CPDs are best kept in heavily planted tanks that mimic their natural habitat of small, shallow ponds with dense vegetation. They are somewhat shy and need appropriate tankmates that won't intimidate them.

Care Requirements

Tank Setup

CPDs thrive in specific nano tank conditions:

• Minimum 10 gallons (20+ recommended for schools)
• Heavily planted - essential for their well-being
• Sponge filter or gentle hang-on-back (avoid strong currents)
• Heater set to 70-74°F (they prefer slightly cooler)
• Dark substrate to show off their colors
• Floating plants for dimmed lighting
• Moss (java moss, christmas moss) for grazing
• Caves and hiding spots

Important: They come from shallow, still waters with dense vegetation. Strong currents stress them.

Water Quality

• Temperature: 68-76°F (20-24°C) - prefer cooler end
• pH: 6.5-7.5 (slightly acidic to neutral)
• Water Hardness: Soft (2-10 dGH)
• Ammonia/Nitrite: 0 ppm
• Nitrate: <20 ppm (keep low)

Maintenance:

• Weekly 20-25% water changes
• They are sensitive to water parameter swings
• Maintain stable, soft water conditions
• Good filtration without strong flow

Feeding

CPDs have small mouths and need tiny foods:

• Micro pellets (0.5mm or smaller)
• Crushed flakes (powder consistency)
• Frozen foods: cyclops, baby brine shrimp
• Live foods: micro worms, vinegar eels, baby brine
• Biofilm: They naturally graze on surfaces

Feeding Schedule: 2-3 times daily, tiny amounts they can consume in 1 minute.

Note: They are slow to accept dry foods initially. Offer live or frozen first.

Behavior & Compatibility

Peaceful but shy nano fish:

• Good Tank Mates:

  • Other small nano fish (Chili Rasbora, Ember Tetra)
  • Pygmy Corydoras
  • Small shrimp (Cherry, Amano)
  • Small Rasboras
  • Peaceful dwarf gouramis

• Avoid With:

  • Large fish (even peaceful ones - they get intimidated)
  • Aggressive fish
  • Fast swimmers that outcompete them
  • Goldfish
  • Angelfish
  • Most tetras (too active or large)

Behavior: School loosely, males spar gently, spend time grazing on biofilm and plants.

Schooling Behavior

Best kept in appropriate numbers:

• Minimum school: 6-8 individuals
• Ideal: 10+ for best behavior and color display
• Male ratio: Males display best colors when competing for female attention
• Tight schooling: They don’t school tightly like tetras but stay in groups

Note: More males = better color displays as they compete.

Breeding

CPDs can be bred in home aquariums:

• Egg scatterers - lay adhesive eggs on plants and moss
• Spawning behavior: Males display vibrant colors and chase females
• Egg protection: Parents will eat eggs - remove or use spawning mop
• Fry care: Very tiny fry need infusoria or vinegar eels first
• Difficulty: Moderate - fry are extremely small

Health Considerations

Generally delicate nano fish:

• Sensitive to parameter swings: Acclimate very carefully
• Ich: Can be affected more severely than larger fish
• Poor water quality: Declines rapidly in poor conditions
• Stress: Easily stressed by aggressive tankmates or strong currents

Prevention:

• Maintain pristine water quality
• Keep parameters stable
• Choose appropriate tankmates
• Provide plenty of hiding spots

Size Considerations

True nano fish:

• Adult size: 0.75-1 inch (very small)
• Sexual dimorphism: Males more colorful, females rounder
• Lifespan: 3-5 years

Appearance

Spectacular coloration for their size:

• Body: Dark blue-black covered in iridescent blue-green “pearls”
• Fins: Bright orange-red with dark edges
• Males: More intense colors, slimmer body
• Females: Duller colors, rounder belly (especially when gravid)
• Sparkling: Under good lighting, they glitter like stars

Tank Maintenance

• Weekly 20-25% water changes
• Gentle water changes (siphon slowly)
• Clean sponge filter regularly
• Prune plants as needed
• Remove uneaten food promptly

Tips for Success

• Start with 10+ gallon tank (more stable parameters)
• Heavy planting is essential for their comfort
• Keep water on the cooler side (70-74°F)
• Use gentle filtration only
• Feed tiny foods appropriate for their size
• Keep in groups of 8+ for best behavior
• More males = better color displays
• Don’t keep with large or boisterous fish
• Maintain excellent water quality
• Dark substrate enhances their colors
• Dim lighting with floating plants

Why “Intermediate” Not “Beginner”

While peaceful and small:

• Sensitive to water parameter changes
• Need specific tank conditions (planted, soft water)
• Small size makes them vulnerable to predation
• Require appropriate nano tankmates
• Fry are extremely difficult to raise
• Can be shy and hide if conditions aren’t right