The giant protuberance on the head of this male Flowerhorn led to this fish's Chinese name luohan, as the hump is reminiscent of the Chinese Buddhist arahat Shou, who also has a swelling forehead (fig.).

Besides the hump, which is officially known as kok or nuchal hump, males differ from females (fig.) by a much thicker and more pronounced mouth, and longer anal and dorsal fins (fig.).