Chromis – Shooling in the Aquarium

Chromis are popular schooling fish from the Pomacentridae family. In aquariums, the most commonly encountered species is Chromis viridis, also known as blue or blue-green chromis. This species is widely distributed throughout the Indo-Pacific region, where it inhabits the warm, shallow waters of coral reefs, typically at depths of up to 12 meters.

Systematics

The Pomacentridae family comprises three similar-looking subfamilies: clownfish (Amphiprioninae), damselfish (Pomacentrinae), and chromis (Chrominae). The most popular chromis in the aquarium hobby is Ch.viridis, although representatives of the genera Dascyllus and Acanthochromis occasionally appear in the trade as well.

Characteristics

Chromis grow to about 5-6 cm in aquariums. Under white light, their coloration is silvery with a hint of green or blue, but in aquariums with predominantly blue-spectrum lighting, they take on a striking blue (occasionally green) hue. One of their greatest attributes is their shoaling behavior. A group of fish in a sufficiently large aquarium will swim together in a mesmerizing silvery-blue display.

In my experience, chromis are relatively peaceful fish, showing less aggression than other members of the Pomacentridae family. However, isolated cases of aggression in individual fish have been reported.

Aquarium

A single chromis or two can be kept in a small aquarium, but to truly appreciate their shoaling behavior, a larger tank with ample swimming space above the reef is essential. In such a setup, a group of several or even a dozen chromis will swim together along the front glass of the aquarium. Thay are active swimmers and brave explorers of the tank’s open spaces. At night, they prefer to hide among SPS corals or in the crevices of rocks.

What do chromis eat?

Thay are not fussy eaters. They readily accept Tropical Marine Power Oceanic Mix flakes and, with a little patience, smaller pellets from the Tropical Marine Power line. Once they detect food, they dash frantically to capture the pieces, creating a lively scene in the aquarium. While this feeding frenzy is entertaining for aquarists, it can make it challenging for more delicate or timid fish to access food.

In general, fish from the Pomacentridae family are relatively easy to care for and thrive in aquariums, primarily serving a decorative role. They are also harmless to invertebrates in the tank.

Bartek Stańczyk