Yellow Boxfish (Ostracion cubicus): Unique Cube-Shaped Marine Fish

The Yellow Boxfish displays a distinctive cube-shaped body with bright yellow coloration and brown spots in juveniles. Adults develop more subdued brown coloration while maintaining their characteristic box shape. These unique fish are known for their curious swimming behavior and interactive personalities.

Expert Only Species: Requires specialized care, massive tank systems, and expert-level aquarium management experience. When stressed, threatened, or injured, Yellow Boxfish release pahutoxin (formerly called ostracitoxin) from skin glands, which can be harmful or fatal to tank inhabitants including themselves. Single-specimen keeping strongly recommended due to toxin risk. Not reef safe.

Size, Growth, and Lifespan:

• Juvenile Size: 2-4 inches when typically purchased
• Adult Size: Up to 18 inches
• Growth Rate: Rapid growth requiring tank size planning
• Lifespan: 10-15 years with proper care

Tank Requirements:

• Minimum Size: 180 gallons (absolute minimum)
• Recommended Size: 240+ gallons for optimal management
• Setup: Open swimming areas with stable rockwork
• Substrate: Sand substrate preferred
• Lid: Secure, tight-fitting lid required (known jumpers)

Water Parameters:

• Temperature: 72-78°F (22-26°C)
• pH: 8.1-8.4
• Salinity: 1.020-1.025 specific gravity
• Water Quality: Excellent filtration and stability required

Diet and Feeding:

Omnivorous species requiring varied nutrition:

• High-quality marine pellets
• Chopped squid, clams, and mussels
• Marine algae and seaweed preparations
• Live/frozen brine shrimp and mysis shrimp
• Feed multiple small meals daily

Behavioral Characteristics:

• Temperament: Generally peaceful and curious
• Activity: Slow, methodical swimming patterns
• Interaction: Often responsive to owner presence
• Social: Best kept as single specimens

Aquaculture Availability:

Primarily available as wild-caught specimens. Aquacultured specimens are not commonly available.

Physical Development:

Juveniles display bright yellow coloration with distinctive brown spots, while adults develop more subdued brown coloration. The characteristic cube shape is maintained throughout their development.

Ideal for: Expert marine aquarists with large systems seeking a unique, interactive centerpiece fish willing to accommodate specialized care requirements.

Expert Only: Items designated as expert only require special care such as a species specific environment, special diet or care, and an expert level, experienced aquarist. Not for beginners. Expert Only items qualify for our live arrival guarantee only, and are exempt from our extended 8 day guarantee.