Cardinalfish are a large family of generally small fish, with almost 350 known species. The length of most species is in the 4 - 17 cm range, though typically they are less than 10 cm. Cardinal fish have large eyes, large mouths, and the dorsal fin is divided into two separate fins with short bases. The lower jaw is often protruding and the tail fin can be either rounded or forked.
This family of fish have very variable colours and patterns, and are often shades of yellow, red, brown or black. Many species are lightly coloured, with a pattern of stripes, spots or dark bars.
Most species of cardinalfishes are nocturnal, territorial fish. They mostly remain hidden during the day amongst coral and in caves, crevices, and under ledges. They usually return to the same 'home' resting spot each day. They are carnivores, feeding on a variety of zooplankton and small invertebrates.
Cardinalfish are paternal mouthbrooders - the males will incubate the developing eggs inside their mouths until the larvae hatch.