Angelicus Catfish (Synodontis angelicus)

Synodontis catfish like this polka-dotted angelicus have a built-in sound system: flexing the base of the pectoral spine against a ridged socket produces an audible squeak, used both as a startle response when handled and, some researchers suspect, to help shoal-mates keep track of each other in low-visibility African rivers. By day it's tucked into whatever cave or driftwood tangle it's claimed; the polka dots come out to patrol after dark.

Care level: Easy · Temperament: Peaceful · Max size: ~9" · Min tank: 55 gal · Diet: Omnivore, sinking pellets/wafers