Damselfish are small, colorful fish commonly found in coral reefs and shallow waters of the tropical and subtropical oceans. They belong to the family Pomacentridae and are known for their vibrant colors, which can range from blue and yellow to orange and black. These fish typically grow to about 3 to 6 inches in length and are often seen swimming in pairs or small groups. Damselfish are territorial and can be quite aggressive, especially when defending their nests. They primarily feed on algae, plankton, and small invertebrates. Their ability to adapt to various environments makes them a popular choice for marine aquariums.