Blue-Green Chromis

The Blue-Green Chromis, also known as the Green Chromis, is one of the most popular and hardy schooling fish in the saltwater aquarium hobby. These small, vibrant fish display beautiful iridescent blue-green coloration that shimmers under aquarium lighting. Active swimmers that occupy the middle and upper water columns, Chromis are peaceful, reef-safe, and excellent for community tanks. They form loose schools and add movement and color to reef aquariums. Their hardiness and peaceful nature make them ideal for both beginners and experienced aquarists.

Care Requirements

Tank Setup

Blue-Green Chromis are active schooling fish:

• Minimum 30 gallons (55+ recommended for schools)
• Open swimming space in mid to upper water column
• Some rockwork for shelter
• Peaceful tank mates
• Protein skimmer
• Moderate to strong flow (they enjoy current)
• Heater to maintain 75-82°F
• Good lighting to show off their iridescence

Important: Keep in groups of 6 or more to encourage schooling behavior and reduce aggression.

Water Quality (Marine)

• Temperature: 75-82°F (24-28°C)
• pH: 8.1-8.4
• Specific Gravity: 1.020-1.025
• Ammonia/Nitrite: 0 ppm
• Nitrate: <20 ppm
• Phosphate: <0.03 ppm
• Calcium: 400-450 ppm
• Alkalinity: 8-12 dKH

Maintenance:

• Weekly 15-20% water changes
• Top off with RO/DI water daily
• Maintain stable parameters

Feeding

Blue-Green Chromis are omnivores and easy to feed:

• Marine flakes and pellets (staple diet)
• Frozen brine shrimp
• Frozen Mysis shrimp
• Copepods (live or frozen)
• Small meaty frozen foods

Feeding Schedule: 2-3 times daily. They are enthusiastic eaters.

Note: They feed in the water column and will readily accept most prepared foods.

Behavior & Compatibility

Blue-Green Chromis are peaceful schooling fish:

• Good Tank Mates:

  • Clownfish
  • Tangs (Yellow, Blue, Kole)
  • Gobies
  • Blennies
  • Cardinalfish
  • Dartfish
  • Firefish
  • Peaceful wrasses
  • Other peaceful reef fish

• Avoid:

  • Aggressive fish (triggers, large angels)
  • Large predatory fish
  • Fish that might eat small fish

Schooling Behavior: Keep in groups of 6+ to see natural schooling. In smaller groups, they may become aggressive towards each other.

Longevity

Blue-Green Chromis are surprisingly long-lived:

• Can live 8-15 years with proper care
• One of the longer-lived small marine fish
• Maintain excellent water quality for maximum lifespan

Health Considerations

Chromis are generally hardy but watch for:

• Marine Ich: Quarantine new fish
• Aggression in small groups: Keep 6+ to spread aggression
• Sudden death syndrome: Sometimes die mysteriously - maintain excellent water quality

Prevention: Always quarantine, keep in proper school sizes, and maintain pristine water conditions.