McCosker’s Flasher Wrasse – Paracheilinus mccoskeri

Quarantine and Conditioning Started on 9/18 - Release Date: 10/8
If you wish to purchase this fish before the release date we will hold the fish for you. Let us know your desired ship date. If there is an issue during the Quarantine process, we will issue a refund.

The McCosker’s Flasher Wrasse (Paracheilinus mccoskeri) is a small, brilliantly colored reef wrasse known for its orange-red body, vivid blue striping, and colorful fins. Males can become especially striking when displaying, intensifying their coloration and spreading their fins in the behavior that gives flasher wrasses their common name.

Despite its elaborate appearance, this is a relatively small wrasse. FishBase records a maximum total length of approximately 8 cm (3.1 inches). The species occurs across the Indo-West Pacific and is associated with outer reef slopes, where it lives around areas of coral, algae, and rubble at recorded depths of approximately 5–50 meters. FishBase

In its natural habitat, Paracheilinus mccoskeri may occur in small mixed-sex groups, typically with females outnumbering males. Females often remain together close to the reef while males move between them. Juveniles can be considerably more secretive and stay close to protective rubble and reef structure. FishBase

For the aquarium, the McCosker’s Flasher Wrasse combines manageable adult size with active swimming behavior and exceptional coloration. It is well suited to a peaceful reef community, but should be provided with hiding places and open swimming space. A secure, tightly fitted cover is strongly recommended for flasher wrasses, which can readily jump from an uncovered aquarium.

This specimen is wild collected from Indonesia and is offered as one of Dr. Mac’s Quarantined and Conditioned Fish.

Care Guide

Scientific Name: Paracheilinus mccoskeri Randall & Harmelin-Vivien, 1977
Common Names: McCosker’s Flasher Wrasse, McCosker’s Wrasse
Family: Labridae
Origin: Indonesia — based on the collection information supplied for this fish
Availability: Wild Collected – Conditioned & Quarantined
Care Level: Easy to Moderate
Temperament: Peaceful
Reef Compatibility: Reef compatible
Minimum Aquarium Size: 30 gallons recommended; larger aquariums provide additional swimming room
Maximum Size: Approximately 3.1 inches (8 cm total length) FishBase
Diet: Carnivore / small-animal feeder
Temperature: 77–82°F (25–28°C)
Specific Gravity: 1.023–1.026
pH: 8.1–8.4

Aquarium Requirements: Provide a mature marine aquarium containing rockwork with numerous retreats as well as open water for swimming. This species naturally remains relatively close to reef structure, so sheltered areas are especially useful when the fish is first introduced. FishBase documents P. mccoskeri on outer reef slopes over coral, algae, and rubble. FishBase

A secure aquarium cover is essential. Small wrasses can jump through surprisingly narrow openings, particularly when startled or during periods of increased activity.

Temperament: McCosker’s Flasher Wrasse is a peaceful species best maintained with other non-aggressive marine fish. Avoid housing it with large or highly aggressive species that may intimidate it or prevent it from feeding normally.

Reef Compatibility: Reef compatible. This species is appropriate for coral aquariums and is not known as a coral predator. Its small adult size and feeding behavior also make it substantially different from larger predatory wrasses that can pose problems for ornamental invertebrates.

Diet and Feeding: Offer appropriately sized foods such as mysis shrimp, enriched brine shrimp, copepods, finely chopped marine foods, and quality small marine pellets. Several smaller feedings can work particularly well for an active small wrasse.

Social Behavior: FishBase documents small mixed-sex groups in the wild, with females generally more numerous than males. Males actively move among groups of females, while juveniles tend to remain more closely associated with protective reef rubble. FishBase

Sand Bed: Unlike many Halichoeres wrasses, flasher wrasses of the genus Paracheilinus do not require a deep sand bed for sleeping. Rockwork containing suitable crevices and sheltered areas is more important.