Blue-green chromis

Lore & Background

Adults of this species reach a maximum length of 10 cm and are a blue-green fish, with individuals appearing iridescent apple-green and light blue. When breeding, males turn more yellowish. The species has 12 dorsal rays, 9 to 11 soft dorsal rays, 2 anal spines, and 9 to 11 anal soft rays. The blue-green chromis is found in tropical and subtropical waters across the Indo-Pacific, including the Red Sea, eastern Africa, Madagascar, the Persian Gulf, Australia, Indonesia, the Philippines, Japan, the Great Barrier Reef, and Hawaii. It also occurs in the eastern Pacific from the Gulf of California to Peru and the Galapagos Islands, with some reports in the Mediterranean Sea. It inhabits coral reefs and lagoons at depths of 1 to 12 metres. In the wild, this fish feeds on phytoplankton, zooplankton, algae, copepods, and amphipods, and also consumes eggs that fail to hatch, feeding by ram jawing. It schools in aggregations around Acropora coral heads. Reproduction involves spawning over sand and rubble; the male prepares a nest shared with several females. The male turns more yellowish during spawning, guards the nest, ventilates it with its fins, and feeds on unhatched eggs to prevent microbial threats. Eggs hatch in 2–3 days.

Reader's Guide

Chromis viridis is a small, schooling damselfish that plays a role in the reef ecosystem by feeding on plankton and algae, and by consuming unhatched eggs to maintain nest hygiene. Its aggregations around Acropora coral heads make it a characteristic sight on Indo-Pacific reefs. In the aquarium trade, the green chromis is relatively inexpensive and is often kept in small schools of odd numbers. Some aquarists have successfully bred this species in home aquariums. It should not be housed with larger predatory fish such as groupers, lionfish, or eels, as they may prey on it. The species is also known as the blue-green chromis, though that name may refer to the close relative Chromis caerulea, which is sometimes considered the same species.

Did You Know?

• Males turn more yellowish when breeding.
• The male guards the nest and feeds on unhatched eggs.