Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. The largest member of the family, the stone triggerfish (Pseudobalistes naufragium) reaches 1 metre (3.3 ft), but most species have a maximum length between 20 and 50 centimetres (7.9 and 19.7 in). On Koh Tao you can see a lot of Titan triggerfish (up to 50 cm.).

The titan triggerfish can move relatively large rocks when feeding and is often followed by smaller fish, in this case orange-lined triggerfish and moorish idol, that feed on leftovers. Triggerfish males are fierce in guarding their territories as having a territory is essential for reproduction. A male’s territory is used for spawning and parental care. Most male territories are located over a sandy sea bottom or on a rocky reef. A single territory usually includes more than one female, and the male mates with all of the females residing in or visiting his territory (polygyny).