One of the family most remarkable on the reefs are the damselfishes or Pomacentridae. They constitute most of the time the majority of fish present on the reefs. They are small (most of them do not exceed 10 cm) and in general gregarious. The majority of the species gather in small shoals from 10 to 200 individuals who never move away far from the coral head where they elected residence.Their food varies according to the species, but a great number eats plankton or grazes tiny algae. These fish are often territorial and defend their space of reef against any intruder, even the man. It is thus in general easy to approach them very close and to observe their behavior.