Blue Boxfish

Ostracion cubicus

Identification	Juveniles are bright yellow with black spots — one of the most charming juvenile fish in the hobby. Adults transition through olive-green tones; males develop blue-gray coloration with yellow markings.
Maximum Length	Up to 17 inches (45 cm)
Origin	Indo-Pacific — Red Sea to Hawaii and Marquesas
Minimum Tank Size	125 gallons
Reef Compatible	With caution

Behavior

Also called the Yellow Boxfish (as a juvenile). The distinctive cube-shaped body is rigid — propulsion comes entirely from fin motion. Generally peaceful but curious. Adults grow considerably larger than most hobbyists anticipate.

Diet & Feeding

Omnivore. Feeds on algae, sponges, tunicates, worms, and small invertebrates. Offer varied marine diet including algae, frozen mysis, and meaty preparations.

Cautions

Releases ostracitoxin when stressed — can kill tank mates. Grows quite large. Not for tanks with aggressive fish. Keep water pristine.