Blue-green Chromis
Common Name
Blue-green Chromis, Chromis
Scientific Name
Chromis viridis (sensu lato for common green chromis/blue-green chromis complex)
📸 Photo Credit:Adobe Stock, By THAIFINN
Blue-green Chromis (Chromis viridis) are planktivores, feeding primarily on zooplankton in the wild, which helps regulate reef ecosystems. Fun Fact: These fish flash brighter colors when schooling together — their shimmer is most vivid in groups of six or more!
Adult Size
3–4 inches (6–10 cm)
Description
The Blue-green Chromis (Chromis viridis) is a shimmering jewel of the reef, known for its peaceful schooling behavior and constant midwater activity. Its iridescent green-blue sheen reflects reef lighting beautifully, harmonizing with both stony coral and soft coral systems.
This species is a favorite among beginners due to its hardiness, adaptability, and lively presence. When kept in groups of six or more, Chromis display natural schooling behavior, darting and flashing color across the tank. Alone, however, they may become stressed and lose confidence, underscoring the importance of maintaining a proper school.
Their peaceful temperament and reef-safe nature make them excellent companions in community aquaria, adding motion and vibrancy without aggression.
Recommended Aquarium Size & Water Parameters
Blue-green Chromis thrive in aquaria with open swimming space and moderate rockwork for shelter. A minimum of 30 gallons is recommended for a small school, though larger tanks allow for more natural schooling behavior and reduced stress.
| Parameter | Range & Notes |
|---|---|
| Minimum Tank Size | 30+ gallons; larger tanks recommended for natural schooling behavior |
| Temperature | 75–82°F (24–28°C); stable tropical range preferred |
| Specific Gravity | 1.023–1.026; reef-safe salinity range |
| pH | 8.1–8.4; slightly basic, supports biological stability |
| Nitrate | <20 ppm (fish-only); <5–10 ppm (reef); lower levels preferred for coral health |
Reef Safety & Compatibility
Blue-green Chromis are reef-safe and peaceful, thriving in groups of six or more. Their schooling behavior adds dynamic motion to reef tanks without threatening corals or invertebrates.
They coexist well with other peaceful species but may be bullied by larger, semi-aggressive fish. Avoid housing them with predatory species, as their small size makes them vulnerable.
| Category | Examples | Notes |
|---|---|---|
| Ideal | Clownfish, Gobies, Firefish, Wrasses, soft corals | Peaceful midwater schoolers; maintain groups for confidence |
| Caution | Large semi-aggressive fish | May be bullied by territorial species |
| Avoid | Large predatory fish | High predation risk |
| Tank Layout Tip | Open swimming area with rockwork for shelter | Keep in schools for best behavior and color |
History & Origin
Native to Indo-Pacific reefs, Blue-green Chromis are among the most commonly available marine fish in the hobby. Both wild-caught and captive-bred strains are widely distributed, with captive-bred specimens offering improved adaptability and sustainability.
Temperament & Personality
Peaceful and schooling, Blue-green Chromis are best kept in groups of six or more. They show their brightest coloration and most natural behavior when swimming together in midwater. Alone, they may become shy, stressed, or lose vibrancy. Their constant motion and shimmering hues make them a lively addition to reef aquaria.
Care Highlights
Diet: Omnivore — readily accepts flakes, pellets, and enriched frozen foods such as mysis or brine shrimp. Multiple small feedings daily help maintain energy and coloration.
Tank Setup: Provide open midwater swimming space with moderate rockwork for shelter. Chromis show their best schooling behavior in tanks with clear swimming lanes.
Breeding: Readily spawns in aquaria; males guard eggs laid on rock or coral rubble until hatching.
Health: Hardy when kept in groups and in stable water conditions. Stress increases when housed singly.
Common Health Issues: Stress-related fading color or hiding when kept alone; susceptible to typical marine parasites (Cryptocaryon, flukes) if quarantines are skipped.
Lifespan: 3–6 years in well-maintained aquaria.
