African Butterfly Fish (Pantodon buchholzi)

African butterfly fish hang motionless right at the surface, wing-like pectoral fins spread wide, waiting for an insect to fall onto the film above them — and when one does, an unusually elastic, upward-hinging mouth snaps shut in a fraction of a second to snatch it. Those same broad fins let it glide briefly above the waterline when startled, which is exactly why any tank holding one needs a tight-fitting lid and not just a loose cover.

Care level: Moderate · Temperament: Peaceful (predatory to small fish) · Max size: ~5" · Min tank: 20 gal, tightly covered · Diet: Carnivore, floating live/frozen foods