About Blue Green Chromis Blue Green Chromis are one of the most popular schooling fish in the marine aquarium hobby, recognised for their bright blue-green to turquoise colouration and active schooling behaviour. They are peaceful damselfish that spend most of their time swimming in the midwater and upper areas of the aquarium. A group creates an impressive natural schooling display, particularly around live rock and coral structures. Blue Green Chromis are relatively hardy compared with many other reef fish and are suitable for established marine aquariums. They appreciate plenty of open swimming space, good water movement and excellent oxygenation. Although often sold as reef-safe schooling fish, groups can develop a hierarchy and some individuals may become aggressive towards weaker fish over time. Providing adequate space and maintaining a sufficiently large group can help distribute aggression. They are primarily planktivores, so a varied diet of small frozen foods, enriched brine shrimp, mysis shrimp and quality marine pellets is ideal. Quick Care Guide Scientific Name: Chromis viridis Common Name: Blue Green Chromis / Green Chromis Family: Pomacentridae Type: Marine Schooling Fish / Damselfish Adult Size: Approximately 8–10 cm Temperament: Peaceful to Semi-Territorial Care Level: Easy Minimum Group: 6+ Minimum Aquarium: 150 L+ Temperature: 24–28°C pH: 8.0–8.4 Salinity: 1.023–1.026 SG Diet: Planktivore / Omnivore Tank Level: Midwater to Upper Levels Reef Safe: Yes Suitable For: Reef aquariums, marine community tanks and schooling displays Frequently Asked Questions How many Blue Green Chromis should I keep? They are schooling fish and are best kept in a group of 6 or more. Larger groups can create a much more impressive display, provided the aquarium is large enough. Are Blue Green Chromis reef safe? Yes. They are generally considered reef safe and will normally leave corals and ornamental invertebrates alone. Are Blue Green Chromis aggressive? They are relatively peaceful for damselfish, but a hierarchy can develop within a group. Some aggression is possible, particularly when the group is too small or the aquarium lacks sufficient space. What do Blue Green Chromis eat? They primarily feed on plankton in the wild. Offer enriched brine shrimp, mysis shrimp, finely chopped marine foods and quality marine pellets or flakes. Do Blue Green Chromis need a large aquarium? Yes. They are active swimmers and benefit from plenty of open water. A larger aquarium is particularly important when keeping a group. Common Mistakes Keeping only 2–3 fish Very small groups can allow aggression to become concentrated on individual fish. A proper group is generally preferable. Not providing enough swimming space Chromis are active open-water swimmers and need plenty of room. Feeding too infrequently Their planktivorous nature means they benefit from regular feeding, particularly in newly established systems. Keeping them with aggressive tank mates Large or highly aggressive fish can stress or prey upon them. Overcrowding the aquarium Groups require sufficient swimming space and filtration to maintain excellent water quality.