The red-tailed triggerfish boasts a robust, oval-shaped body with a distinct color scheme that evolves as it matures. Juveniles exhibit a sleek black body adorned with numerous small, iridescent blue spots, creating a shimmering "glass-like" effect that inspired its nickname. As they grow into adults, the tail fin transforms into a vivid orange or red, contrasting sharply with the dark body, which may fade to a deeper brown or gray. Growing up to 30 centimeters in length, it features a large mouth with powerful, beak-like teeth designed to crush the shells of its preferred prey: crustaceans, mollusks, and sea urchins. Its dorsal fin includes a prominent first spine that can be locked into place for defense, a characteristic trait of triggerfish.

In its natural habitat, Melichthys vidua is often found in shallow, sunlit reefs, lagoons, and rocky outcrops at depths of 2–30 meters. It is a territorial species, particularly during the breeding season, when males fiercely defend their nesting sites from intruders. Divers may observe its curious nature as it approaches to investigate, though it remains wary and quick to retreat into crevices if threatened. This triggerfish plays a vital role in reef ecosystems by controlling sea urchin populations, preventing overgrazing on coral and maintaining biodiversity.

Despite its resilience, the red-tailed triggerfish faces challenges from human activities. Overfishing for the aquarium trade and casual fishing pressure in some regions have impacted local populations. Additionally, habitat degradation from coral bleaching and coastal development threatens the reefs it calls home. While currently listed as "Least Concern" on the IUCN Red List, conservation efforts such as marine protected areas and responsible tourism practices are essential to ensure its long-term survival. As a symbol of the reef’s vibrant beauty, Melichthys vidua reminds us of the urgent need to protect these fragile ecosystems and the diverse species that inhabit them.