Jack Dempsey

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: sand.

Behavior

Plant interaction: digs around roots.

Feeding

Carnivore-leaning omnivore. Pellets (cichlid pellets, not community food), frozen krill, frozen shrimp, frozen bloodworm, frozen silversides, and live earthworms. Will eat vegetable matter but doesn't seek it out. Feed once or twice daily. Adults are messy eaters that produce a lot of waste; strong filtration is essential. Live food triggers hunting behavior and keeps the fish mentally stimulated.

Compatibility

• Named after the boxer for a reason. Jack Dempseys are pugnacious, territorial, and will fight other cichlids for dominance. They're not mindlessly aggressive (they won't chase neon tetras around the tank), but they won't share territory with similar-sized or similar-shaped fish.
• Tankmates need to be tough, fast, or large enough to hold their own: silver dollars, large catfish (raphael, pleco), large loaches, and other robust Central American cichlids (firemouths, severums). Avoid anything delicate, slow, or similar in shape to another cichlid.
• A bonded pair is aggressive enough to clear a 300-liter tank of all other fish during breeding. If keeping a breeding pair in a community, the tank needs to be large (400 L) with distinct zones.
• The "electric blue" Jack Dempsey variant is smaller, less aggressive, and more fragile than the standard form. It's effectively a different fish in terms of temperament despite being the same species.

Origin and habitat

Rocio octofasciata, the Jack Dempsey, is a robust Central American cichlid from the Atlantic slope, ranging from the Rio Actopan area of Veracruz in Mexico south through Belize and Guatemala to the Ulua basin in Honduras. It lives in slow, often murky water, swamps, canals, ditches, and sluggish rivers over soft bottoms with plant cover, and has established introduced populations in several countries outside its native range. The fish was named after the heavyweight boxing champion of the 1920s for its pugnacious temperament. It spent years in the catch-all genus Cichlasoma before Schmitter-Soto erected the genus Rocio for it in 2007; the species name octofasciata refers to the banded body pattern. Adults are dark with rows of iridescent blue-green spangles across the flanks and gill covers. The fish reaches around 25 cm at the top end, though many top out closer to 18 to 20 cm, with males larger than females. The familiar Electric Blue Jack Dempsey is a colour mutation fixed by selective breeding; it stays smaller, is more delicate, and is noticeably calmer than the standard fish, so the two are best treated as different animals for stocking.

Breeding

A substrate spawner with fierce biparental care. The pair cleans a flat rock or scrapes a pit and the female lays a large clutch, commonly several hundred eggs and up to around 800, which both parents guard. After hatching the fry are shifted to a pit and watched over until they are free-swimming roughly a week later. The defence during brood care is among the most aggressive of any aquarium cichlid; a guarding pair will go at anything that comes near, whatever its size. New pairs sometimes eat their first spawns and settle down with practice. Breeding itself is not hard, given a flat surface and stable water; the real work is housing the aggression, which usually means a dedicated breeding tank. Fry start on infusoria, then baby brine shrimp and microworms.

Common problems

Aggression and adult size are the recurring problems. A single fish in a large enough tank is manageable, two males is a fight, and a breeding pair will dominate everything around it. Tank size is often underestimated, since juveniles are sold small at a few centimetres but reach around 20 cm within a year. Like other large Central American cichlids kept in poor conditions, they can develop hole-in-the-head erosion, which is linked to diet, water quality, and stress, so clean water and a varied diet are the best prevention. The electric blue form needs extra care: it grows more slowly, stays smaller, and is more prone to illness than the standard fish.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size