Filefish are rhomboid-shaped fish with with deep keeled bodies and can appear very similar to triggerfish, their close relatives. Filefish have very thin (laterally compressed) bodies, small snouts and mouths with projecting incisor teeth. The eyes are located high on the head. Filefish vary in size from around 20 cm up to about 60 cm for the largest species, the scribbled filefish, which is often found at the dive sites around Koh Lanta.
This family of fish have a slender, retractable dorsal fin spine on the top of the head, and in most species, there is a second, smaller dorsal fin spine, which is used to lock the first spine into an erect position. The remaining fins are simple, soft fins, with small pectoral fins and a short, fan-shaped tail fin. Scales are very small, giving the skin a rough leathery feel, hence the other common name 'leatherbacks'.
Filefish are bottom-dwelling and can be found solitary, in pairs, or small groups. Filefish are slow swimmers, in part due to their small, soft fins. Some species feed on algae, others on small invertebrates, including sponges, plants, gorgonians and hydrozoans. Some species eat corals and zooplankton.