Blue Koran Angelfish (Pomacanthus semicirculatus)

Blue Koran Angelfish start out with concentric blue-and-white rings across a dark body — a pattern so striking it's often mistaken for a completely different species — before settling into a solid, scaled blue-green as an adult. It carries the same defensive cheek spine every true angelfish is named for, ready to flare in a territorial dispute. A dramatic, long-term showpiece for a big, established tank.

Care level: Moderate · Temperament: Semi-aggressive · Max size: ~15" · Min tank: 180+ gal · Diet: Omnivore, marine algae + meaty foods