Yellow Boxfish

A boxy, slow-grazing reef fish whose bright yellow, black-spotted juvenile coloring fades to a duller mustard-to-blue-grey as it matures past 45 cm. It swims by sculling its fins rather than flexing its body, so it can't outrun trouble — and like every boxfish, it releases a lethal skin toxin (ostracitoxin) when stressed, injured or dying that can wipe out an entire tank, itself included. Keep it alone, in a large tank, and never with aggressive or nippy tankmates.