The Rhomboid Fairy Wrasse, Cirrhilabrus rhomboidalis, is a Micronesian species collected from the Marshall Islands and reefs around Palau, Saipan, and parts of the Federated States of Micronesia. Males carry an ivory-to-golden body overlaid with purple and blue shading, with fine intricate lines tracing the head and flanks and a caudal fin shaped into the diamond or rhomboid outline that gives the fish its name. Females wear the same pattern in more subdued tones. When a male displays to females or rivals, the yellow intensifies and the indigo markings deepen dramatically. Adults reach roughly 4 inches.

In the wild, this wrasse lives along deep outer-reef slopes and rubble zones, typically recorded between about 35 and 100 meters. Because it originates from dim, deep water, it should be acclimated gradually to very bright reef lighting rather than dropped straight under intense fixtures. Plan on a 70-gallon aquarium or larger for a single adult, with additional volume if a male will be housed with females. Combine broad open swimming lanes with substantial rockwork, rubble, crevices, and caves that offer both daytime shelter and sleeping sites; a sand bed is not required, and brisk flow suits the species well.

A tight, gap-free canopy is mandatory. Startled individuals bolt upward with little warning, and any open overflow or unscreened gap in the lid becomes a hazard. Numerous low-level hiding places and calm, less-active tankmates both reduce the frequency of those panic runs and help a new arrival settle in. Care level is moderate, largely because of the lighting transition, the jumping risk, and the attention required during the first weeks in a new system.