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FishFreshwaterIntermediate
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Jack Dempsey

Rocio octofasciata

The Heavyweight Brawler of Central America (20-25 cm / 8-10 inches). Named after the legendary 1920s boxing champion, this fish boasts a bulldog-like face, a thickly muscled body, and a famously terrible temper. But it is an absolute visual showstopper: a dark, almost pitch-black body heavily armored with hundreds of massive, blindingly bright neon cyan, gold, and emerald 'spangles' (scales) that look like glowing sequins. He destroys tanks, digs massive craters, and will relentlessly bully anything that gets in his way.

Water Temperature

22 - 26 °C

pH Value

6.5 - 8

Water type

Freshwater

Tank level

Bottom and middle

Adult size

25 cm

Minimum tank volume

>= 300 L

Minimum group

>= 1

GH

5 - 20 dGH

KH

2 - 10 dKH

TDS

95 - 400 ppm

Conductivity

148 - 625 uS/cm

Species description

Geographical Origin and Habitat: Broadly distributed in the swamps, slow-moving warm rivers, muddy canals, and overgrown weed-choked pools of Southern Mexico, Honduras, and Guatemala. They are extremely rugged pioneers of nature. They prefer murky, turbid water with muddy bottoms where they can hide under massive tangles of roots, ambushing prey and tearing up the bottom looking for crustaceans.
Taxonomy and Morphology: A gargantuan, incredibly thick Central American cichlid (genus Rocio, which translates to 'Dew', describing the brilliant spangled spots on its body like morning dew). Males grow massively, easily hitting 25 cm (10 inches) and weighing incredibly heavy. The face is iconic: a steep, angry, sloping forehead leading down to a massive, muscular, extremely powerful jutting jaw filled with strong teeth designed to crush snail shells and rip apart smaller fish. Their fins develop long, vicious-looking trailing points as they age.
Social Behavior: The 'Bully of the Block'. It completely earns its boxer's name. As tiny juveniles, they are incredibly shy, hiding in caves. But as they hit 5 inches, the monster awakens. They are aggressively, violently territorial. A male will claim a massive cave and fiercely patrol a 3-foot radius around it. Any fish that crosses the invisible line gets violently head-butted or bitten. THEY ARE TANK DESTROYERS: They are obsessive diggers ('earth-movers'). They will dig a giant crater down to the bare glass of your tank overnight, uproot every single plant you carefully placed, and use their mouths to angrily throw rocks at the glass if they are bored.
Coloration and Sexual Dimorphism: A walking jewelry box. When an adult male is fired up or angry, his base body turns a deep, dark charcoal, mahogany, or velvet pitch-black. Over this dark canvas, his entire face, gills, flanks, and fins are absolutely encrusted with enormous, highly reflective, glowing metallic NEON BLUE, AQUAMARINE, and GOLD scales (spangles). They literally flash in the light like sequins. Males are much larger and have significantly more spangles. WARNING: The highly expensive 'Electric Blue Jack Dempsey' (EBJD) is a captive-bred mutant with a solid, blazing neon-blue body; while stunning, they are genetically ruined, incredibly fragile, and notoriously drop dead suddenly from weak immune systems.

Care, breeding and tankmates

Aquarium Setup: A heavily armored prison is required. A single adult needs a 120 cm tank, but if keeping it with other monsters, 150 cm (5 feet / 100+ gallons) is the absolute minimum. DO NOT PLANT IT: They will shred real plants into floating garbage in an hour. Use heavy, massive, smooth river boulders and giant, water-logged driftwood stumps. Build them a giant cave out of thick PVC pipes or heavy terracotta pots (make sure they are secured with silicone, or the Dempsey will physically push them over, smashing your glass). Use thick sand or heavy gravel, because they will dig craters everywhere. Secure your glass heaters in a sump or a titanium cage, or he will break it during a tantrum.
Diet and Feeding: A bottomless, vicious Omnivore. They will eat anything that falls in the water. Feed massive, high-protein cichlid pellets (floating or sinking) as the absolute staple. To beef them up and explode their blue spangle colors, you MUST feed them heavy, meaty treats 3 times a week: giant earthworms, live gut-loaded crickets, chunks of raw shrimp, frozen Krill, and tilapia fillets. DO NOT FEED THEM GOLDFISH: Pet store feeder fish carry horrific parasites and fatal enzymes that destroy the Dempsey's liver over time.
Water Quality: The 'Bulletproof' Cichlid. They are incredibly hardy and tolerate a massive range of water conditions. Hard water, soft water, it doesn't matter. pH 6.5 to 8.0+. Temperature 22-30°C (72-86°F). BUT DO NOT BE LAZY: Just because they survive in dirty water doesn't mean they thrive. Because they eat so heavily and poop so massively, if you do not use giant canister filters and do 50% weekly water changes, the skyrocketing Nitrates will cause 'Hole in the Head' disease, literally rotting giant white craters into their beautiful faces until they die.
Compatibility and Cohabitation: THE 'MONSTER TANK' EXCLUSIVE. Never mix a Jack Dempsey with peaceful community fish, Tetras, Guppies, Angelfish, or small Corydoras. The Dempsey will torture them, rip their fins off for fun, and swallow them whole in the night. THEY CAN ONLY LIVE IN A 'THUG TANK': House them strictly with other giant, heavily armored, bad-tempered Central/South American bruisers. Good tank mates include large Oscars, brutal Green Terrors, aggressive Convict Cichlids, giant armored Plecos (over 10 inches long), or massive Silver Dollars. However, do NOT put two adult male Dempseys in the same tank, or they will lock jaws and fight to the death.
Aquarium Breeding: Brutal Substrate Spawners. Buying an adult pair often results in the male murdering the female if she isn't ready. You must buy 6 babies and wait for them to bond over a year. The bonded pair turns pitch black and violently claims half the aquarium, brutally attacking the Oscars or Plecos, driving them into the upper corners. They clean a flat rock, lay up to 800 eggs, and fiercely guard them. Once the tiny fry hatch, the parents will dig deep trenches in the sand and physically carry the babies in their mouths, spitting them into the 'bunker' to hide them from predators. If you stick your hand in the tank, the male will charge and bite you hard.
Risks and Diseases: 1. THE 'WIPEOUT' TRAGEDY: Mixing a juvenile Dempsey into a peaceful community tank; a year later, the owner wakes up to find every single other fish floating dead, missing eyes and fins, because the Dempsey hit sexual maturity and claimed the entire tank. 2. Heater Electrocution: Smashing the fragile glass heater against the glass while doing a massive 're-decorating' dig, electrifying the tank. 3. Fatal 'Hole in the Head' (Hexamita) disease caused entirely by the owner's laziness in skipping massive weekly water changes.

Geographic Origin and Distribution

Broadly distributed in the swamps, slow-moving warm rivers, muddy canals, and overgrown weed-choked pools of Southern Mexico, Honduras, and Guatemala. They are extremely rugged pioneers of nature. They prefer murky, turbid water with muddy bottoms where they can hide under massive tangles of roots, ambushing prey and tearing up the bottom looking for crustaceans.

Origin

Central America and Caribbean

Fish profile

Temperament
Semi-aggressive
The Jack Dempsey is well known for its belligerent and aggressive temperament. It actively and aggressively defends its chosen territory. Heavy decoration can help manage aggression by breaking lines of sight.
Diet
Omnivore
The Jack Dempsey is primarily carnivorous but accepts a variety of foods. High-quality cichlid pellets should form the staple diet. Supplement with live or frozen foods like bloodworms and brine shrimp.
Life expectancy
10-15 years
Under optimal captive care, the Jack Dempsey cichlid typically enjoys a lifespan of 10 to 15 years. Achieving this longevity depends on providing a large aquarium with excellent filtration and stable water chemistry, as they are sensitive to poor water quality and organic waste buildup. A balanced diet containing high-quality proteins and essential vitamins helps prevent nutritional deficiencies and strengthens their immune system. Minimizing stress by providing ample hiding spaces and avoiding overly aggressive tankmates will also extend their lifespan.
Adult size
25 cm
The catalog's scalar value is 25 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 25 cm for this species, recorded as total length (TL). The taxonomic record consulted is Rocio octofasciata (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
Sex ratio
Pair
They are best kept as a single male-female pair in most setups. Keeping multiple males usually leads to severe aggression and territorial disputes. Carefully monitor the female for signs of harassment.
Feeding frequency
Twice daily
Adults should be fed once a day to prevent obesity. Juveniles require two to three smaller meals daily to support growth. Avoid overfeeding to maintain optimal water quality.
Bioload
This species generates a significant bioload due to its size and hearty appetite. Powerful filtration is required to process the heavy waste output. Regular large water changes are also essential to maintain good water quality.
Flow
Stagnant
It prefers a moderate flow in the aquarium environment. Strong currents are not necessary but good circulation is. Ensure there are calmer areas for the fish to rest comfortably.
Reproduction
Oviparous
These cichlids are substrate spawners and excellent parents. They become highly aggressive when breeding and raising fry. Flat rocks or large slate pieces should be provided as spawning sites.
Compatibility & tankmates
It is highly aggressive and territorial in nature. It should only be kept with other large, robust cichlids. Small tankmates will likely be bullied, injured, or eaten.
Tank level
Middle/Bottom
It mainly inhabits the middle and bottom levels of the tank. It likes to stay near caves and structural cover. It rarely swims at the very top of the water column.

Scientific Parameters & Models

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026
Trophic level
3.5 ± 0.51 se
Resilience
High (less than 15 months)
Phylogenetic uniqueness (PD50)
0.5625
Bayesian Length-Weight
a = 0.02692, b = 3.02
VulnerabilityLow vulnerability (15 / 100)

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Last updated: 05/13/2026
Jack Dempsey (Rocio octofasciata) Care Guide & Tank Setup | Atlarium