It is laterally compressed and its length can reach 20 cm (7.9 in). The colour of the body and the large oral cavity is very variable, but is usually mottled and spotted yellow, green, and brown on a paler background, and the fins often have several dark streaks or bands. The fish can change colour rapidly, from light to dark and back again.[3] The body and the fins are covered with many weed-like protrusions, but other than these, the skin is smooth without dermal spines.