Bicoloured Foxface (Siganus uspi)
The Bicoloured Foxface (Siganus uspi), also known as the Uspi Rabbitfish, is an eye-catching marine species endemic to the coral reefs of Fiji. It belongs to the Siganidae family and is known for its bold black and white colouration, venomous spines, and algae-grazing behaviour. Though a peaceful species, it requires adequate space and careful handling due to its defensive capabilities.
Key Information
• Small fish safe ✅ Yes (generally peaceful)
• Small invertebrate safe ✅ Yes (primarily herbivorous)
• Coral safe ⚠️ With caution (may nip at soft and LPS corals if underfed)
• Minimum tank size 475 litres (125 gallons)
• Adult size Up to 24 cm (9.4 inches)
• Diet Primarily herbivorous, grazing on algae
• Be aware of Venomous dorsal, anal, and pelvic fin spines; handle with caution
Appearance and Colouration
The Bicoloured Foxface is instantly recognisable due to its high-contrast pattern:
• Body Colouration
The front half is black, while the back half is bright white. The dividing line runs diagonally from the dorsal fin down towards the pectoral fin.
• Head Markings
The snout is black, blending into the eye area, giving it a masked appearance.
• Juvenile vs. Adult
Juveniles have a sharper contrast in their bicolour pattern, while adults may develop a slightly faded white region.
Natural Habitat and Behaviour
In the wild, Siganus uspi inhabits shallow coral reefs and coastal lagoons, where it grazes on algae and contributes to reef health. It is diurnal, spending the day actively foraging before seeking shelter among branching corals or rock crevices at night.
• Habitat
Typically found at depths of 2 to 25 metres, preferring clear, coral-rich environments.
• Defensive Camouflage
Can change colour when stressed or at night, becoming a mottled brownish-grey to blend into surroundings.
Tank Requirements and Water Parameters
• Minimum Tank Size 475 litres (125 gallons)
• Water Parameters
• Temperature 24°C – 28°C (75°F – 82°F)
• pH 8.1 – 8.4
• Specific Gravity 1.020 – 1.025
• Aquascaping
• Provide plenty of live rock for grazing and hiding spots.
• Allow open swimming space for its active nature.
• Lighting Moderate to high to encourage algal growth for natural grazing.
• Water Movement Moderate, replicating natural reef currents.
Diet and Feeding
As an herbivorous grazer, the Bicoloured Foxface requires a high-fibre, algae-rich diet.
• Primary Diet
• Marine macroalgae and algae sheets (e.g., nori).
• Blanched spinach, romaine lettuce, and seaweed.
• High-quality herbivore pellets and flakes.
• Supplementary Foods
• Occasional mysis shrimp or brine shrimp.
• Feeding Frequency
2–3 times per day, ensuring continuous access to algae for grazing.
Compatibility and Social Structure
• Temperament
• Peaceful with most tank mates but may show mild aggression toward other rabbitfish.
• Suitable Tank Mates
• Compatible with tangs, angelfish, clownfish, and wrasses.
• Avoid housing with aggressive species that may bully or stress it.
Important Considerations
• Venomous Spines
• The dorsal, anal, and pelvic spines contain venom, which can cause painful stings.
• Always be aware of their location during tank maintenance.
• Reef Compatibility
• Mostly reef-safe, but may nip at corals if underfed.
• Algae Control Role
• Helps maintain low algae levels in large aquariums.
Summary
The Bicoloured Foxface (Siganus uspi) is a boldly patterned, algae-grazing species that thrives in large, well-maintained marine aquariums. With proper diet and stable water conditions, it serves as both a beautiful and functional addition, helping to prevent algae overgrowth. However, its venomous spines and potential for coral nipping require careful management.