The McCosker's Flasher Wrasse or Paracheilinus mccoskeri is a flasher wrasse from the western Indo-Pacific, where they are found from the east coast of Africa to Fiji, and are most common in the waters of the Malay Archipelago. A truly stunning species, a generally peaceful disposition combined with hardiness and the added benefit of staying small makes P. mccoskeri truly one of the best suited wrasses for keeping in a reef aquarium. They grow to a size of approximately 3-inches in length.
P. mccoskeri should be kept in a minimum aquarium size of a 20gal Long (likely larger if you intend to keep a harem) fitted with a tight lid. In the wild, these wrasses are found along reef slopes and rubble zones, and therefore the aquarium should contain plenty of live rock rubble piles or rockwork to retreat into. Additionally, they need a tank with a nice sandbed, as they will dive into and hide within the sand when frightened, and burrow within it or the rockwork, secreting a mucus cocoon, to sleep at night.
Optimal conditions for P. mccoskeri are; pH 8.1-8.4; salinity 1.020-1.025; and temperature 72-78 degrees F.