Distribution
The fish is native to Mexico and Honduras, where it is found in slow-moving waters, such as swampy areas with warm, murky water, weedy, mud- and sand-bottomed canals, drainage ditches, and rivers. It is also established as an introduced species in Australia, the USA and Thailand (presumably as an aquarium escapee).
Ecology
The Jack Dempsey natively lives in a tropical climate and prefers water with a pH of 7-8, a water hardness of 9–20 dGH, and a temperature range of 22–30 °C (72–86 °F). It can reach up to 25 cm (10 in) in length. It is carnivorous, eating worms, crustaceans, insects and other fish. It can eat small/young platies when it is three inches long.
Reproduction
Jack Dempseys lay their eggs on the substrate (the bottom of the aquarium or pool). Like most cichlids, they show substantial parental care: both parents help incubate the eggs and guard the fry when they hatch. Jack Dempseys are known to be attentive parents, pre-chewing food to feed to their offspring. However, it is not uncommon for them to eat their fry when the breeding pair are overly disturbed or something in their environment is wrong.
Morphology
The coloration changes as the fish matures from a light gray or tan with faint turquoise flecks to a dark purple-gray with very bright, iridescent blue, green, and gold flecks. Their colors change under stress. The dorsal and anal fins of mature males have long, pointed tips. Females lack these exaggerated tips.
In the aquarium
The fish is popular a popular aquarium fish, due to its striking appearance and personable mannerisms. It, like most cichlids, is considered "aggressive", but can get along in a well-populated tank, tending to be more territorial if kept with only a few other fish, therefore allowed to easily establish and defend a "territory" in the tank.
Trivia
In 1997 the San Francisco Chronicle reported that a man had died when he put a Jack Dempsey into his mouth as a joke: the fish presumably erected its fin spines to avoid being swallowed, a characteristic cichlid anti-predator response, and became wedged in the man's throat.
In a second season episode of Homicide: Life on the Street, a Jack Dempsey is recovered at the scene of a murder, and is taken home by an unsuspecting Detective John Munch, who intends to give it to his tropical fish-collecting girlfriend as a present. As a surprise, he places the fish in her aquarium, where it proceeds to devour $4,000 worth of her fish before being removed. Munch later refers to the fish as an "assassin" who "uses piranhas as toothpicks."
