The Monacanthidae family includes marine fish known as filefish, which are related to triggerfish and found mainly in tropical and subtropical waters. Their name comes from their rough, sandpaper-like skin, which was traditionally used as a natural file by local populations in some regions. They are easily recognized by their flattened bodies, small mouths and especially their dorsal fin, which has a large first spine that they can raise either for defense or to wedge themselves into crevices. Filefish are most commonly found on tropical reefs, where they feed on algae, small invertebrates and sometimes sponges. Their ability to change color to blend in with their surroundings helps them avoid predators and ambush prey.