Jack Dempsey

Overview

The Jack Dempsey (Rocio octofasciata) is a classic big-personality New-World cichlid, named after the boxer for good reason. Adults are stocky, muscular fish of 20–25 cm decorated with iridescent blue-green spangles, and they are genuinely aggressive and territorial. Kept honestly — in a big tank, alone or as a bonded pair — they are hardy, long-lived and full of character. Kept in an undersized community tank, they become a problem for everyone else.

Tank & water

Be realistic about space from day one. A single adult needs at least 280 litres (75 gallons), and a pair or any tankmates push that much higher. See our large-tank guide.

• Temperature: 22–28 °C from a robust, guarded heater.
• Water: pH 6.5–7.5, moderate hardness; test regularly with a kit.
• Strong filtration: these are messy fish — oversize the filter and keep nitrate down with generous water changes.
• Aquascape: sand substrate, rock and wood caves, and sight breaks that let fish avoid one another.

Feeding

Jack Dempseys are carnivores. Feed a quality large-cichlid pellet as the staple, supplemented with frozen or fresh meaty foods such as prawns, mussel and earthworms. Avoid feeder fish, which risk disease, and don’t rely on mammalian meat like beef heart. Big appetites mean heavy waste, so match feeding with filtration and water changes.

Tankmates

Best kept alone or as a single bonded pair. If you attempt tankmates, choose large, robust fish that can’t be swallowed or bullied — big plecos or similarly sized, tough cichlids — in a very large tank with plenty of cover. Avoid all small, slow or long-finned fish. Before adding anything, sanity-check the load with how many fish in an aquarium and watch for overstocking.

Common mistakes to avoid

• Buying the juvenile without the 280-litre-plus tank the adult needs
• Trying to keep one in a mixed community of small fish
• Under-filtering a big, messy, heavy-feeding cichlid
• Ignoring escalating aggression instead of separating fish

For a much smaller, more community-friendly cichlid, the firemouth or convict are gentler alternatives that still deliver cichlid character in a far more manageable package.