Boxfish - Yellow

Yellow Boxfish (Ostracion cubicus)

Overview

The Yellow Boxfish (Ostracion cubicus) is a distinctive and eye-catching marine fish known for its bright yellow coloration with small black spots. Native to the Indo-Pacific, including the Red Sea, East Africa, and the Great Barrier Reef, it inhabits coral reefs, lagoons, and sandy areas.

This species is slow-moving, peaceful, and reef-compatible under proper care, making it a unique addition to larger marine and reef aquariums.

Aquarium Requirements

• Minimum Tank Size: 125 gallons (475 litres)

• Temperature: 24–27°C (75–81°F)

• pH: 8.1–8.4

• Specific Gravity (Salinity): 1.020–1.025

• Alkalinity: 8–12 dKH

• Ammonia & Nitrite: 0 ppm

• Nitrate: < 10 ppm

• Aquascape: Provide open swimming areas with live rock for shelter and hiding

Yellow Boxfish require a large, stable aquarium with ample swimming space due to their slow, deliberate movements and active grazing behavior.

Diet and Feeding

Yellow Boxfish are omnivorous and benefit from a varied diet:

• High-quality marine pellets or flakes

• Frozen foods such as mysis shrimp, brine shrimp, and chopped seafood

• Occasional algae-based foods for vegetable matter

Feed small portions 2–3 times daily. Boxfish have small mouths, so food size and frequency are important for proper nutrition.

Temperament and Compatibility

Yellow Boxfish are generally peaceful and slow-moving. They can coexist with other non-aggressive species but should be monitored as adults can release a toxic substance when stressed.

Tankmate Recommendations:

• Suitable: Non-aggressive reef fish such as tangs, gobies, and anthias

• Avoid: Aggressive or fin-nipping species

Stress should be minimized with stable water conditions, adequate space, and gentle handling.

Reef Compatibility

⚠ Caution – Potentially Reef Safe

While Yellow Boxfish generally coexist with corals and invertebrates, they can release a toxin (ostracitoxin) when stressed or threatened, which may harm other tank inhabitants. Careful monitoring and quarantine are recommended.

Additional Information

• Maximum Size: Up to 45 cm (18 inches) in the wild; smaller in aquaria

• Lifespan: 10+ years with proper care

• Difficulty Level: Moderate to Advanced

• Natural Behavior: Slow-moving, peaceful, grazers on algae and small invertebrates

• Origin: Indo-Pacific reefs, including the Red Sea, East Africa, and the Great Barrier Reef