Hartzfeld's Cardinalfish

Found in small schools, during the day amongst coral, debris, and in the arms of long-spined sea urchins, over shallow reef flats and lagoons, dispersing at night hunting for food.
They feed nocturnally on crustaceans, small fish, and zooplankton.

Males incubate their eggs inside their mouths, as the egg masses increase in size they can be found with wide open mouths where they shift the eggs around to aerate the egg masses.