Boeseman's rainbowfish

Melanotaenia boesemani is a strikingly colorful freshwater fish of the family Melanotaeniidae, endemic to the Ayamaru Lakes region in the Bird's Head Peninsula of West Papua (Indonesian New Guinea). Adults reach about 8–11 cm in length and are among the most popular aquarium rainbowfishes. Males display a spectacular bicolored pattern: the anterior half of the body is brilliant blue-gray to violet, while the posterior half transitions to vivid orange-yellow or golden, separated by a variable zone of blending. Females are less colorful, showing more subdued olive-green to silver tones. The body is deep, laterally compressed, and ovate, with two dorsal fins (a short anterior one and a longer posterior one), a forked caudal fin, and large eyes. In the wild, M. boesemani inhabits clear, alkaline, hard-water lakes with dense aquatic vegetation. They are omnivorous, feeding on small invertebrates, algae, and organic matter. Spawning occurs over extended periods; males display intensified colors during courtship, and adhesive eggs are scattered among fine-leaved vegetation. The species is listed as Endangered by the IUCN due to its extremely restricted natural range, habitat degradation, and historical overcollection for the aquarium trade. Captive breeding programs now supply most aquarium specimens, reducing pressure on wild populations.