The Undulate Trigger, Balistapus undulatus, also known as the Orange-Lined Trigger, Orange-Tailed Trigger, and Orange Tailed Triggerfish, features a characteristic orange tail with yellow-orange vertical striping patterns.. Sometimes, the Undulate Trigger can make an audible grunting sound. It is hardy, shy, and can be quite aggressive. They can bite fingers during feeding so be careful. The Undulate Trigger eats a varied carnivorous diet and will also chew or carry on small rocks in the tank. When frightened, it will wedge itself into the live rock crevasses.