thumb|right|Golden Base type flowerhorn
Flowerhorn cichlids are ornamental aquarium fish noted for their vivid colors and the distinctively shaped heads for which they are named. Their head protuberance is formally called a nuchal hump. Like blood parrot cichlids, they are hybrids that exist in the wild only because of their release. Flowerhorns first emerged for sale on the aquarium market in Malaysia in the late 1990s and soon became popular in many countries in Asia. They are commonly kept by hobbyists in the US, Asia, and Europe. Numerous cast-off flowerhorns have been released to the wild, especially in Singapore and Malaysia, where they have become an invasive pest animal. Their importation is banned in Australia.
Origin
Flowerhorn breeding dates to 1993. Taiwanese and Malaysian peoples admired fish with protruding heads, known as 'kaloi' or 'warships', found in the western part of the nation. The slightly protruding forehead and long tail of cichlids were prized in Taiwanese society as bringing luck in geomancy. By 1994, red devil cichlids (typically Amphilophus labiatus) and trimac cichlids (A. trimaculatus) had been imported from Central America to Malaysia and the hybrid blood parrot cichlid had been imported from Taiwan to Malaysia. These fish were then bred together, marking the birth of the flowerhorn.
Arrival in the West
When luohans were first imported to the US, there were only two varieties of these fish for distribution: the flowerhorn and the golden base.
Flowerhorn cichlids are subject to several diseases, including hole-in-head disease, "ich", and digestive blockages.
Varieties
thumb|200px|General flowerhorn variety classification, containing several subsets of varieties (strains) from different countries and breeders
The original flowerhorn hybrid stock are referred to as luohans (from the Chinese word for the Buddhist concept of ). The four main derived varieties are zhen zhu, golden monkey, kamfa, and the golden base group, Like most other cichlids, flowerhorns are aggressive and can breed quickly, competing with and eating native fish.
Flowerhorn breeding
Finally, another issue with regard to flowerhorns is the dilution of genetic lineages, since flowerhorns are hybrids and not true species.