Jack Dempsey Stats
Minimum Tank Size: 55 Gallons (208 Liters)
Care Level: Moderately Difficult
Water Conditions: 6.5-8.0 pH and Soft to Moderately Hard
Temperature: 72-77°F (22-25°C)
Maximum Size: 8 inches (20 cm)
The Jack Dempsey (Rocio octofasciata) is a popular species of cichlid, known for its belligerent nature. Named after the famous 1920s boxer, Jack Dempsey, these fish were named after him because they shared his aggressiveness and strong facial features. Its scientific name has changed several times, and it was previously known as Cichlasoma, Heros, and Archocentrus. There is also an Electric Blue Jack Dempsey variant available in the aquarium hobby, which appears to be a mutation, and they tend to be slightly smaller than natural Jack Dempseys.
Native to Guatemala, Mexico, Belize and Honduras, these fish are found along the Atlantic coastal region. Jack Dempseys inhabit slow-moving water and are found in streams, rivers, lakes, canals, and bogs. In recent years, they have become established as an invasive species in the United States, Russia, and Thailand.
In the home aquarium, these fish usually live at least 10 years, with some living up to 15 years in a well-maintained fish tank. A full-grown adult may reach up to 8 inches (20 cm) in length.
It should come as no surprise that a fish named after an aggressive boxer, doesn’t do well with other fish. Jack Dempseys are notoriously territorial, generally intolerant of other fish, and will often bite tankmates. It’s recommended to keep mature, bonded pairs together, where they will form family units with their offspring.
The minimum recommended aquarium size for a pair of bonded Jack Dempseys is 55 gallons (208 liters), but as they breed easily and often, they will soon require a much larger aquarium. To comfortably house a growing family of Jack Dempseys, a 75-gallon (284 liters) fish tank should be provided. These fish are susceptible to poor water quality and should only be introduced into a fully cycled – preferably mature – aquarium.
The substrate should be a thick layer of fine sand, with several large, flat stones that can be used as spawning locations. Several caves and large pieces of driftwood should be provided as hiding places for these fish. It’s important to ensure any decorations and rocks are placed in stable locations. These fish burrow continuously and will often dig the base out from underneath items in the aquarium, causing them to topple over and potentially damaging the glass.
Since they burrow relentlessly, it’s usually best to avoid most live plants. However, floating plants do reasonably well with these fish, as do any plants that can be attached to ornaments, like Java moss and Java ferns.
When choosing a filter, a hang-on-back filter is usually the most economical choice for an aquarium containing Jack Dempseys. Alternatively, aquariums this large are an excellent candidate for canister filters, but while very effective, they tend to be much more expensive. My personal recommendation for a filter is the Aquaclear Power Filter, and I use these filters without issue in most of my aquariums.
Jack Dempseys are omnivores in the wild but have a strong appetite for live foods. They should be fed a diet comprised of a high-quality flake food, as well as regular offerings of lightly blanched vegetables, live foods, and non-acidic fruit. I personally recommend Hikari Cichlid Pellets, which is a high-quality food that helps to bring out the natural colors of Jack Dempseys.
When it comes to live foods, they can be fed mosquito larvae (illegal to culture in some areas), daphnia, gut-loaded brine shrimp, bloodworms, blackworms (or tubifex in Europe), and cyclops.
Jack Dempseys are substrate spawners and breed in the open. These fish form pairs and if an aquarium has a bonded pair, then breeding will normally happen without any intervention from the aquarist. However, if breeding does not occur, then the fish can be conditioned by feeding them live foods until spawning occurs.
Prior to breeding, the parents will clean a flat space – usually a smooth rock or a space on the aquarium glass – before they deposit between 500-800 eggs on the surface. The parents will then carefully guard the eggs until they hatch, at which time the fry will be moved to a pit where they will be carefully guarded and kept by the parents.
While the parents will attempt to feed their fry, the newly hatched fish will still need specialized fry food. It’s best to feed the fry infusoria for the first 48 hours, and then move them onto either baby brine shrimp or microworms. Commercial fry food can also be used for the fry.
As with many other new cichlid parents, Jack Dempseys may consume their first few broods. But after spawning several times, they usually get the hang of parenting. Though it’s been reported if they are overly disturbed, they may eat their fry.
Jack Dempseys reproduce regularly and in large numbers. It’s important to have a plan in place for potentially hundreds of juvenile fish, as they can quickly overwhelm an aquarium.
While it’s recommended to keep Jack Dempseys in a species only aquarium, they can be kept with other, similarly sized aggressive fish. But it will require a very large aquarium for it to work. A few cichlids that may work are Convicts, Firemouths, Green Terrors, and Salvinis. Also, Silver Dollar fish generally work well, as do large semi-aggressive catfish like pictus catfish.