Mustard Guttatus Tang

The Mustard Guttatus Tang (Acanthurus guttatus), also known as the Whitespotted Surgeonfish, is a striking Indo-Pacific saltwater fish recognized for its deep-bodied profile and distinctive patterning. Adults typically display a gray-brown to olive body with pale vertical bands across the front half, numerous small white spots covering the rear body and fins, and bright yellow pelvic fins. Subtle mustard and bronze tones can become especially noticeable under strong reef aquarium lighting.

Native to shallow, high-energy reef flats and seaward reefs throughout the Indo-Pacific, this species is naturally adapted to areas exposed to strong surge and water movement. It spends much of the day grazing algae from hard reef surfaces, making it a natural fit for mature marine aquariums with established rockwork.

The Mustard Guttatus Tang is best suited to a large reef aquarium or fish-only aquarium with excellent oxygenation, strong filtration, and generous swimming space. Its active behavior, unusual coloration, and constant grazing make it an impressive display fish for appropriately sized systems.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 180 gallons
Temperament: Semi-aggressive
Diet: Herbivore
Reef Safe: Yes
Region: Indo-Pacific
Scientific Name: Acanthurus guttatus

Tank Requirements

Provide a spacious aquarium with long, open swimming lanes and mature live rock arranged to create abundant grazing surfaces, caves, and sheltered resting areas. The aquascape should remain open enough for this active surgeonfish to move freely without being confined by dense rockwork.

Strong water movement is especially appropriate for this species because it naturally inhabits shallow reef environments exposed to surge and currents. Excellent oxygenation, efficient biological filtration, and consistently stable water quality are important for long-term success.

No specialized substrate is required. Mature rockwork with natural algae growth is highly beneficial, allowing the fish to graze between scheduled feedings. A secure aquarium cover is recommended because startled tangs can make sudden, powerful movements and may jump.

Diet and Feeding

The Mustard Guttatus Tang is primarily herbivorous and naturally grazes filamentous and other reef-associated algae from hard surfaces throughout the day.

Offer dried marine algae or nori regularly, along with spirulina-based pellets, high-quality herbivore pellets, marine algae preparations, and frozen herbivore blends. Mysis shrimp, enriched brine shrimp, and other small marine foods can be offered occasionally for variety, but vegetable-based foods should remain the foundation of the diet.

Several smaller feedings throughout the day are ideal when practical. Keeping algae sheets available for extended grazing helps support the species' natural feeding behavior.

Temperament and Tankmates

This species should be considered semi-aggressive, particularly around other tangs and surgeonfish. Territorial behavior is most likely toward similarly shaped species and other members of the genus Acanthurus competing for the same swimming and grazing areas.

Keeping a single specimen is the safest choice for most home aquariums. Multiple tangs should only be considered in substantially larger systems with extensive swimming space, multiple grazing zones, and carefully planned introductions.

Suitable tankmates include many wrasses, clownfish, anthias, chromis, rabbitfish, angelfish, and other appropriately sized marine fish that are not excessively aggressive.

Reef Compatibility

Reef Safe: Yes

The Mustard Guttatus Tang is considered reef safe and primarily grazes algae rather than feeding on corals or ornamental invertebrates. It is generally suitable for established reef aquariums containing soft corals, stony corals, clams, ornamental shrimp, crabs, and snails.

Its grazing activity can be beneficial in a reef aquarium, but regular supplemental feeding is still essential even when natural algae is present.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain stable, well-oxygenated water and avoid rapid changes in temperature, salinity, or pH. Consistency is more important than targeting a single exact number within these ranges.

Common Considerations

• Requires a large aquarium with substantial open swimming space.

• Benefits from strong water movement and excellent oxygenation.

• Needs frequent access to marine algae and other vegetable-rich foods.

• May become territorial toward other tangs, especially similarly shaped Acanthurus species.

• Possesses sharp scalpel-like spines near the base of the tail, so care should be taken during capture and transfer.