Filament-finned wrasse

Geographical Origin and Habitat: Cirrhilabrus filamentosus is native to the tropical waters of Indonesia, including Java, Bali, Flores, and Timor. It inhabits seaward coral reefs, sandy transition zones, and rubble fields, typically found swimming at depths between 10 and 35 meters in areas exposed to moderate tidal currents.

Taxonomy and Morphology: Belongs to the family Labridae and the genus Cirrhilabrus (commonly known as fairy wrasses). It reaches a maximum adult length of approximately 8 centimeters. The primary morphological feature, from which its scientific name is derived, is a long, single filament extending from the middle of the dorsal fin in adult males.

Social Behavior: An extremely active, peaceful, and diurnal fish that spends the daytime swimming in open water searching for food. It is non-aggressive toward other tankmates, except possibly other male fairy wrasses. At night or when threatened, it retreats into rockwork or substrate, sleeping inside a protective mucus cocoon.

Coloration and Sexual Dimorphism: Displays spectacular coloration and significant sexual dimorphism. Adult males feature a bright red-orange upper body, while the lower flanks and throat are a vivid electric blue or purple, accented by long yellow pelvic fins. Females are smaller, showing a more uniform pinkish-orange coloration and lacking the elongated dorsal filament.

Aquarium Setup: Requires an aquarium of at least 150 liters with plenty of open swimming space. The layout should include live rock structures arranged to form caves and passages for night shelters. A fine sand substrate is recommended, as they may dive into the sand when startled. Moderate to strong water flow is beneficial.

Diet and Feeding: A zooplanktivore. In the aquarium, it should be fed high-quality frozen foods like mysis shrimp, brine shrimp, chopped krill, and copepods. It easily acclimates to dry flakes and pellets. It is best to feed small portions two to three times daily to support its active swimming habits and fast metabolism.

Water Quality: Requires stable marine parameters: water temperature between 24 and 28 °C, pH levels from 8.1 to 8.4, and a specific gravity of 1.020 to 1.025. Efficient filtration is needed to keep nitrate levels low. Regular use of activated carbon is advised to keep the water clear and free of yellowing compounds.

Compatibility and Cohabitation: An excellent addition to reef aquariums (reef safe). It can be kept in a harem consisting of one male and several females, introducing the females first. It coexists peacefully with most community reef fish, but avoid keeping it with highly aggressive wrasses or large predators.

Aquarium Breeding: Breeding in captivity is extremely difficult. In nature, they are pelagic spawners that release eggs and sperm into the water column during rapid vertical spawning rushes. There are no major records of successfully raising the fry in a home aquarium setting.

Risks and Diseases: Like all fairy wrasses, this species is an exceptional jumper and can easily leap out of open tanks when startled or during courtship. A tight-fitting lid or a fine mesh cover is mandatory. It can be susceptible to common skin parasites if stressed during introduction.