How big does Jack Dempsey get?

Jack Dempsey reaches an adult standard length of 15–20 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.

What water does Jack Dempsey need?

22–28 °C, pH 6.5–8, 5–20 dGH. At 6 °C wide it is one of the more forgiving ranges.

What is the smallest tank for Jack Dempsey?

At least 200 L, and no shorter than 100 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is not a schooling fish, so a single specimen or a pair is fine.

What is Jack Dempsey like to keep?

Temperament: aggressive. Difficulty: beginner. It occupies the bottom and is carnivore. With plants it is "Eats plants".

Can Jack Dempsey be kept with its most common tank mate?

The checker returns "Not recommended together". Jack Dempsey and Guppy is a recorded conflict in this atlas. Predation, territorial fighting or conspecific aggression is the usual outcome, and a bigger tank does not change it.

G-01 / 27Freshwater

Jack Dempsey杰克邓普西（蓝宝石）

Rocio octofasciata · Cichlidae

A Central American cichlid spangled with blue-green flecks that reaches 20 cm and only tolerates tough cichlids.

Illustration to come

G-01 / 27 · Jack Dempsey Rocio octofasciata

SpecificationsFish atlas

Name: 杰克邓普西（蓝宝石）
Scientific name: Rocio octofasciata
Family: Cichlidae
Origin: Central America (southern Mexico to Honduras)
Adult size: 15–20 cm
Temperament: Aggressive
Diet: Carnivore
Water level: Bottom
Level: Beginner
Min. tank: 200 L
Min. length: 100 cm
Plant safe: Eats plants

Water requirementsFreshwater

Temp.22–28 °C

pH6.5–8

Hardness5–20 dGH

Units: temperature in °C, hardness in German degrees (dGH / dKH), marine salinity as specific gravity at 25 °C, volume in litres. These are the values recorded for the species and do not follow the site unit switcher.

Keeping notes

1About 20 cm and aggressive: keep only similar-sized cichlids with plenty of separate territories.
2Darkest and fiercest when spawning, chasing tankmates into corners, so use a tank over 100 cm.
3Digs and uproots, so build with rock and wood rather than fine-leaved plants.
4Does well at 22-28 °C in neutral, fairly hard water; omnivorous with a meaty lean on pellets and prawn.

Check a tank mate

Jump straight to the verdict for Jack Dempsey against this one — no need to pick it again.

Frequently asked questions

How big does Jack Dempsey get?: Jack Dempsey reaches an adult standard length of 15–20 cm (excluding the caudal fin). Size the tank for that, not for the juvenile you bring home — the difference is often several times over, and upgrading later costs more than buying once.
What water does Jack Dempsey need?: 22–28 °C, pH 6.5–8, 5–20 dGH. At 6 °C wide it is one of the more forgiving ranges.
What is the smallest tank for Jack Dempsey?: At least 200 L, and no shorter than 100 cm. That is the floor for long-term keeping, not for short-term survival: volume buys water stability and length buys swimming room, and neither substitutes for the other. It is not a schooling fish, so a single specimen or a pair is fine.
What is Jack Dempsey like to keep?: Temperament: aggressive. Difficulty: beginner. It occupies the bottom and is carnivore. With plants it is "Eats plants".
Can Jack Dempsey be kept with its most common tank mate?: The checker returns "Not recommended together". Jack Dempsey and Guppy is a recorded conflict in this atlas. Predation, territorial fighting or conspecific aggression is the usual outcome, and a bigger tank does not change it.