Gem Tang

The Gem Tang (Zebrasoma gemmatum) is a rare, highly sought‑after Indian Ocean surgeonfish known for its black body covered in brilliant white “gem‑like” spots and a contrasting yellow tail. It is considered one of the most exclusive tangs in the hobby and requires a large, stable, mature reef system. 🐠 Identity & Appearance • Scientific name: Zebrasoma gemmatum • Common names: Gem Tang, Gemmatum Tang, Mauritius Tang, Spotted Tang • Coloration: Deep black or dark blue body with bright white spots resembling stars or gemstones; yellow tail is typical. • Adult size: 8–9 inches (20–22 cm). • Rarity: Naturally limited to Mauritius, Madagascar, and nearby regions, contributing to its high price and exclusivity. 🌍 Natural Habitat • Range: Western Indian Ocean—especially Mauritius and Madagascar. • Environment: Coral‑rich reefs and rocky slopes with strong water movement and high oxygen. • Depth: Commonly 33–200 ft (10–60 m). • Behavior in the wild: Constant grazer that moves through open lanes while using reef structure for shelter. 🧠 Temperament & Behavior • Temperament: Semi‑aggressive, especially toward other tangs or similarly shaped fish. • Activity: Highly active swimmer; requires long horizontal space. • Reef‑safe: Yes—primarily herbivorous and does not harm corals. 🏡 Aquarium Requirements • Minimum tank size: • 130 gallons minimum (per Reeflings) • 180 gallons+ strongly recommended for long‑term success (per multiple care guides). • Aquascape: • Large amounts of live rock for grazing • Open swimming lanes • Caves and hiding areas to reduce stress and aggression • Water parameters: • Temp: 74–82°F • Salinity: 1.023–1.026 • pH: 8.1–8.4 • Flow: Moderate to strong; high oxygenation is important. • Difficulty: Moderate to advanced—requires stable, mature systems and careful acclimation. 🍽️ Diet • Primary diet: Herbivore—feeds mainly on marine algae. • In captivity: • Nori sheets • Spirulina‑based pellets • Herbivore blends • Occasional mysis or meaty foods as supplements • Feeding style: Frequent small feedings to mimic natural grazing. 🧬 Lifespan & Health • Lifespan: Up to 30 years reported with proper care. • Common issues: Stress during shipping, ich/velvet susceptibility, and aggression toward other tangs. • Best practice: Quarantine and slow, controlled introduction to display tanks. 🪸 Compatibility • Good tankmates: Wrasses, anthias, rabbitfish, peaceful reef fish. • Use caution with: Other Zebrasoma tangs or similarly shaped species due to territoriality.