Blueside wrasse

Geographical Origin and Habitat: Cirrhilabrus cyanopleura is widely distributed in the Indo-West Pacific. Its range includes the Ryukyu Islands (Japan), the Philippines, Palau, Indonesia, Taiwan, and the northern part of the Great Barrier Reef. It inhabits outer coral reefs, steep reef slopes, and wide sandy or rubble zones rich in corals at depths ranging from 5 to 30 meters. It is often found hovering in mid-water in groups numbering dozens of individuals, grazing above the coral reef in areas swept by currents rich in zooplankton.

Taxonomy and Morphology: Belonging to the family Labridae, genus Cirrhilabrus (commonly known as fairy wrasses). It has a slender, elongated, and slightly laterally compressed body, with a rounded or slightly lanceolate caudal fin in adult males. The eyes feature a specialized 'bi-focal' cornea that facilitates the detection of tiny planktonic organisms. It reaches a maximum length of about 12 centimeters. Like other wrasses of this genus, it has the ability to change sex during its lifetime.

Social Behavior: It is an active, gregarious, and peaceful species. It spends daytime hours constantly swimming in the water column above the reef. Dominant males control large territories where a harem of females resides. During courtship, the male performs spectacular nuptial displays, intensifying his colors within seconds. At night, or if threatened, they retreat into the rockwork, wrapping themselves in a light cocoon of protective mucus to hide their scent from predators.

Coloration and Sexual Dimorphism: This species exhibits highly pronounced sexual dimorphism and a very variable color pattern. Females and juveniles are a uniform orange-red or pinkish color with a small black spot on the caudal peduncle. Adult males feature an iridescent blue-greenish body with a characteristic purple or dark blue patch on the side, just behind the pectoral fin, and a head that can shade from yellow to bright orange.

Aquarium Setup: Requires a spacious aquarium of at least 250 liters (approx. 65 gallons) with ample open swimming space. The setup must include live rock arranged to form caves and passages where the fish can hide. An ABSOLUTE requirement for this species is a tight-fitting lid or a fine mesh screen on the tank: as fast and easily spooked swimmers, they are notorious jumpers, and any open gap could be fatal.

Diet and Feeding: An active zooplanktivore. The diet must consist mainly of high-quality small frozen protein foods, such as mysis, brine shrimp, copepods, and finely chopped krill. It also readily accepts dry foods in pellets and flakes. Due to their fast metabolism and constant motion, it is advisable to feed them two or three times a day to prevent rapid loss of body mass.

Water Quality: Requires stable parameters: temperature 24-27°C (75-81°F), pH 8.1-8.4, specific gravity 1.021-1.025, and low nitrates and phosphates. High oxygenation of the water, achieved through wavemakers and an efficient protein skimmer, is crucial. Regular water changes maintain the stable trace element levels necessary for the fish's health.

Compatibility and Cohabitation: It is a peaceful and completely reef-safe fish, in no way bothering corals or invertebrates. It coexists very well with other peaceful reef species such as clownfish, gobies, anthias, and surgeonfish. It is possible to keep a group by introducing a single male and multiple females of the same species. Avoid cohabitation with aggressive or territorial fish such as large marine groupers or lionfish.

Aquarium Breeding: Breeding in the aquarium is extremely rare and complex. In the wild, they practice pelagic group or pair spawning. The male lures the female toward the surface with fast, undulating movements before releasing gametes. Larval development is hindered by the need for appropriate microscopic live prey in the earliest stages of life, making breeding confined to scientific research.

Risks and Diseases: The main risk is jumping out of the water, which makes a protective cover mandatory. They are hardy fish but can contract external parasites under severe introduction stress. A quarantine period is recommended to monitor behavior. Providing adequate hiding places reduces acclimation anxiety and promotes rapid coloration of the males.