🐟 AquaticCare difficulty: BeginnerLegal complexity: Low
Green Chromis
Chromis viridis · also called Blue Green Chromis, Blue-Green Damselfish, Green Puller
A shimmering blue-green schooling damselfish that catches light beautifully among coral branches. Hardy and inexpensive, it is one of the most popular beginner reef fish, though in-school hierarchy losses are common.
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Quick facts
| Size | Reaches about 3-3.5 in (8-9 cm) as an adult. |
| Lifespan | 8–15 years |
| Social needs | group |
| Native region | Indo-Pacific |
| Origin | Old World |
| Climate | 🌴 Tropical |
| Water type | 🌊 Marine |
| Family | Pomacentridae |
| Genus | Chromis |
Part of the Damselfish & Chromis
Small, hardy, often brilliantly colored reef fish of the family Pomacentridae, including the schooling chromis and the bolder damsels. Popular, inexpensive, and largely reef-safe, they range from peaceful planktivores to feisty, territorial species.
Habitat & space requirements
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Habitat & enclosure
Green chromis are active mid-water swimmers and are best kept in a shoal, so provide at least a 30-gallon tank for a small group, with 55 gallons or more strongly recommended for a school of six or more. Open swimming space in the upper and mid water column is important, along with live rock and branching corals that mimic the SPS coral thickets they shelter among in the wild.
Maintain stable tropical reef parameters: temperature 72-82 F (22-28 C), pH 8.1-8.4, salinity 1.020-1.025 specific gravity, and moderate flow. They are fully reef-safe, leaving corals and invertebrates alone, and their gentle movement among coral branches can even help keep detritus from settling.
Substrate
A standard reef sand bed of fine aragonite works well; these mid-water schoolers spend little time on the bottom, so substrate choice is mostly aesthetic and for buffering. Open swimming space above the rockwork matters more than the floor.
Equipment & setup
Reef conditions with a protein skimmer, good flow, and live rock; sg 1.024-1.026 and 72-78 F. Because they shoal, provide a larger tank (30+ gallons) with branching rock or coral for the group to retreat into at night.
Diet
Green chromis are planktivores that feed on zooplankton in the open water. In the aquarium they readily accept a varied omnivore-leaning diet of frozen mysis and brine shrimp, copepods, marine flakes, and small pellets. Feed small portions one to two times daily, ideally dispersed in the current so the whole group can pick from the water column.
They are enthusiastic, easy feeders. Vitamin-enriched and color-enhancing foods help maintain the iridescent blue-green sheen and good body condition across the group.
Behavior & temperament
Green chromis are among the most peaceful damselfish and are generally good community and reef tankmates. The main behavioral challenge is internal: as a group establishes its pecking order, dominant individuals harass subordinates, and over time schools often dwindle to one or two fish as weaker members are stressed out. Starting with a larger group (six or more, ideally more) and providing ample space and cover helps disperse this aggression.
They are constantly active, schooling and darting among the rocks and corals, which makes them lively display fish. Mature breeding individuals may become a bit bolder, but their small size keeps any aggression minor. A roomy tank with structure for retreat keeps the group stable.
Health
Green chromis are hardy and disease-resistant for marine fish, but they are still susceptible to ich and velvet, especially after shipping stress. Quarantine new fish and acclimate carefully. The most common practical issue is hierarchical aggression within the school, which causes chronic stress, hiding, refusal to feed, and gradual attrition of subordinate fish.
Prevent losses by keeping a sufficiently large group, providing plenty of swimming room and hiding places, and maintaining stable water quality. Avoid mixing them with overly aggressive damsels that disrupt the school. A varied diet and low-stress environment support their notably long potential lifespan.
Tips, DIY & hacks
Buy an odd-numbered group of six or more at once: in small numbers they bully each other down to a single survivor as a pecking order forms. They are hardy, reef-safe, and inexpensive, making them a classic first marine fish; feed small frequent meals of mysis and enriched brine to keep the whole school colored up and competing peacefully.