Green chromis

What it is

The green chromis is a species of damselfish characterised by its iridescent apple-green and light blue colouration. Adults reach a maximum length of ten centimetres. The fish possesses twelve dorsal rays and nine to eleven soft dorsal rays. Its anal fin features two spines and nine to eleven soft rays. This small reef dweller is easily recognised by its vibrant hues and compact size.

Where it lives

This species inhabits tropical and subtropical waters across a vast geographic area. In the Indian Ocean, it is present in the Red Sea, Gulf of Aden, eastern Africa, Madagascar, Seychelles, Persian Gulf, Arabian Sea, Maldives, Sri Lanka, Andaman Sea, Australia, and Indonesia. Pacific populations extend from the Gulf of Thailand and Indonesia to China, Taiwan, Japan, Great Barrier Reef, New Zealand, New Caledonia, Polynesia, Melanesia, and Hawaii. Eastern Pacific records span from the Gulf of California south to Peru and the Galapagos Islands. Occasional reports exist for the Mediterranean Sea. They live in coral reefs and lagoons at depths of one to twelve metres.

How it lives

Green chromis form schools around Acropora coral heads. Their diet consists mainly of phytoplankton, zooplankton, algae, copepods, and amphipods. They feed using a ram jawing technique. Unhatched eggs also serve as a food source. This feeding behaviour helps maintain nest hygiene. Larger predatory fish such as groupers, lionfish, and eels pose a threat to these small damselfish. They are not suitable tankmates for such predators due to the risk of predation.

Breeding and life cycle

Spawning occurs over sand and rubble substrates. The male prepares a nest that is shared with several females. During this period, the male turns more yellowish in colour. He guards the nest and ventilates the eggs with his fins. The large clutch hatches within two to three days. Males consume any eggs that fail to hatch. This prevents the unhatched eggs from becoming breeding grounds for microorganisms that could threaten the remaining healthy clutch.

Fish and people

The green chromis is a common choice for marine aquariums. It is relatively inexpensive and hardy. Aquarists keep them in small groups of odd numbers to encourage natural schooling behaviour. A single specimen requires a tank of at least thirty-eight litres, while a small school needs a minimum of one hundred and ten litres. Some hobbyists have successfully bred this species in home aquariums. Care must be taken to avoid housing them with larger predatory fish.

Relatives and look-alikes

The blue-green chromis name is sometimes applied to Chromis caerulea, also known as the blue puller. This close relative is occasionally considered conspecific with the green chromis. Confusion between the two names may arise due to their similar appearance and taxonomic proximity.

Questions people ask about Green chromis

Good reading and sources

• Chromis viridis on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data