Cardinalfish are mainly marine creatures although a few species are found in brackish and freshwater environments. They are small fish, usually under 10 centimetres long and can be recognized by their big eyes, large mouth and the division of the dorsal fin into two separate fins.
They are usually described as nocturnal but this really means that by day, they shelter in small caves or dark crevices on the reef. Some species live in a more exposed position, but on darker dive site like a muck site with dark sad. These species tend to take refuge in the spines of an urchin or the tentacles of a coral. Cardinalfish tend to be homebodies, picking a nice looking patch on spot on the reef and then sticking to it. Males are mouthbrooders, the hold brood their eggs inside the mouth until they are ready to hatch.
Cardinals are not regarded as threatened although many habitats are under threat. The exception is the Banggai cardinalfish.
