Wikipedia:
Flowerhorn cichlids are ornamental aquarium fish noted for their vivid colors and the distinctively shaped heads for which they are named. Their head protuberance, or kok, is formally termed a "nuchal hump." Like blood parrot cichlids, they are man-made hybrids that do not exist in the wild. First developed in Malaysia, Thailand, and Taiwan, they became very popular with Asian fish hobbyists. They are also kept by hobbyists in the US and Europe, but their importation is banned in Australia. Some cichlid hobbyists have questioned the impact of flowerhorn breeding programs and their impact on the health and reproduction of the animals, and on natural fish species.