female (male has yellow between stripes)
The Scissortail sergeant or Striptailed damselfish (Abudefduf sexfasciatus, family Pomacentridae) is a large damselfish. It earns its name from the black striped tail and sides, which are reminiscent of the insignia of a military Sergeant, being similar to those of the Sergeant Major damselfish. It grows to a length of about 16 cm (6 in).
Scissortail seargents are coral reef dwelling fish, living at depths of up to 15 m (50 ft) in tropical reaches, often living in a group surrounding a single head of coral. They are found on reefs in the Indo-Pacific area. The fish feed upon the larvae of invertebrates, zooplankton, smaller fishes, crustaceans and various species of algae. They are preyed upon by some members of the Labridae and Serranidae families. They lay their eggs in patches on a firm substrate and guard them vigorously until they hatch. (Text source: Wikipedia)