Jack Dempsey Fish Stats InfographicJack Dempsey fish, also known as Rocio octofasciata, is a hostile cichlids species commonly found in the southern Mexican rivers. They are stern-looking, yet they have fascinating body colorations.

Most fish-keeping enthusiasts term these aggressive tropical water breeds hardy because they can be bullies.

Nonetheless, read about the Jack Dempsey fish to learn crucial care tips on managing them in your community aquarium.

Jack Dempsey Fish Stats

Jack Dempsey Fish stats comprises of quick stats and classification stats.

– Quick stats

Jack Dempsey size 10 inches
Tank size (minimum) 48 inches(for juvenile)
Strata Bottom to middle
PH 7.0 -8.5
Hardness Medium hard to very hard
Temperature (77-82)°F or (22-30)°C

– Classification stats

Order Perciformes
Suborder Percoidei
Family Chiclidae
Genera Cichlasoma
Quick stats:
Listed tank sizes are the minimum
Size: 10 inches  (25.0 cm)
Tank: 48 inches, larger for adults
Strata: Bottom, middle
PH: 7 to 8.5
Hardness: Medium hard to very hard
Temperature: 77° to 82°F  (22 to 30°C)

– Origin

The Jack Dempsey fish is originally from central and Northern American rivers such as Belize, Honduras, Guatemala, southern Mexico, Yucatan, and the Atlantic coast. However, aquarist has confirmed to have seen them in shallow, warm, and slow-moving water bodies of Australia and Thailand. The rivers contain a lot of greenery and plants with a murky appearance.

– Name

Jack Dempsey fish: it got the name jack Dempsey from the 1920’s famous boxer due to its aggressive nature.

  • Rocio octofasciata: the name “Rocio octofasciata” is of Spanish and Latin origin. The biologist who discovered it named it in honor of his wife the “morning dew,” which translates in Spanish as Rocio. Also, he claims the iridescence spots on the body of Jack Dempsey fish looks like dew.
  • octofasciata are two Latin words; “octo,” meaning eight, and fascia, meaning stripes; making its complete translation eight striped. However, only the adult jack Dempsey has eight stripes; the juvenile has more markings.

– Body Form

Jack dempsey fishIn a wild habitat, full-grown Jack Dempsey can measure up to 10 inches. However, the tank-bred Jack Dempsey fish growth rate may drop to give it a total length of about 6 inches, depending on its simulated habitat and care. In addition, the females are generally smaller in size.

The Jack Dempsey cichlid size is compacted yet oval-shaped like a disk and has pointy fins.

The fully grown Jack Dempsey male has a slight bump on their forehead and a fan-like caudal fin. In comparison, the males have longer dorsal and anal fins than the females.

– Coloration

The juvenile Jack Dempsey has pale grey coloration with a greenish spot while the transition of the mature one to a deep purple and grey tint with cyan specks. However, Jack Dempsey has a wide range of coloration based on mood and maturity.

  • Mood: it appears dark-colored when it is stressed, aggressive, or breeding. You would assume it is a blackjack Dempsey fish at any of those times.
  • Maturity: the juvenile jack Dempsey has about ten to eleven faint stripes at a very young age. However, it fades off gradually and becomes eight markings and more noticeable as they mature. The marks tend to show on a female or juvenile’s back, forehead, and abdomen but appear only on the forehead of a full-grown male jack Dempsey fish.

The female jack Dempsey is less colorful than the male species. Their primary color is dark grey, but the glow from its scales makes it look bright. Furthermore, their scales, opercula bones, and fins have an iridescence outlook. It means that their coloration changes between a blue hue, a golden glow, or a greenish-blue color based on the light you use to look at it.

The male has a centered dark-colored spot on its body and tail, while the spot shows on the edge of the females’ gill and dorsal fin. They also have a parallel black-colored band that starts from their gill region to the dark spot in the center of their body. Meanwhile, the female jack Dempsey has more minor iridescence specks on its scales, unlike the male.

The juvenile cichlids have eyespot patterns on their tail and side regions, but the adult fish do not possess it or fades off as it grows. The Jack Dempsey has a greyish-bronze tint in its eyes, a pale blue lip color, and its dorsal fins have some reds at the edge.

– Behaviour

Jack Dempsey is a resilient species; you would find them in habitats where other tropical fishes would not thrive. They are hardy, particularly to a beginner fish-keeper, and can be highly aggressive. Their aggression is common with the male jack Dempsey, whose reason is a territorial reaction. However, they would eat smaller fish in a tank without remorse.

They are more likely to bully tank mates in less populated community tanks. It is because they have more space to swim about and can easily detect the weakest link. The Jack Dempsey fish is a medium to bottom strata dweller and would spend most of its time there. They lose all their color and specks when they are struggling in their simulated habitat. They also like to dig their substrates.

– Life Span

The Jack Dempsey fish lifespan is up to 10 years. Some tank-breed cichlids even survive up to 15 years, depending on their care and feeding.

Jack Dempsey Fish Care Guide

The Jack Dempsey fish care has to be almost perfect so you can ensure it lives up to its average life expectancy. So we have explained them in various categories according to their needs.

1. Aquarium Decor

You should put in a lot of vegetation, so the tank mimics its natural habitat. A jack Dempsey tank needs different forms of decor like driftwood and other cave-like shelters. The more caves and crevices to hide, the less aggressive they are. It gives it personal space to rest, hide and make their territories. Be sure to space out tank decorations, or the jack Dempsey fish would use them as landmarks and claim an un-even portion of the tank.

The Jack Dempsey are omnivores and would likely eat up the aquarium plant, but the Sagittaria is sturdy and tough. You can put in aquarium toys like a castle or a ship as a shelter suggestion for your jack Dempsey pet fish. Use potted aquarium plants like water wisteria and java fern because they can switch up and decide to burrow through the roots of the tank’s greenery. Perform proper research so you do not plant a poisonous plant variant out of ignorance.

2. Filter

They like slow-moving water, so you would not need a powerful filter that pumps strong currents. Frequent water changes of about 20 percent of the tank content can reduce ammonia and nitrates. You should do it at least once a month, so the nitrate levels do not surpass 40 mg/l.

Other water changing tips:

  1. Do not change all the water in the jack Dempsey aquarium at a time because you can get rid of the good bacteria contained in the tank.
  2. You can opt for a weekly 10 percent water change or 40 percent monthly.

A juvenile jack Dempsey is most likely to survive a poor water environment. But once they are up to four years, it can get fatal if their water contains toxic chemicals. In some cases, the adult jack Dempsey develops a disease called hexamitiasis. So clean your fish tank with only warm water; do not add any form of soap product.

3. Substrate

They like to burrow at the bottom of rivers in the natural habitats; they dig through the sands or muds. To simulate this experience for these middle to bottom strata cichlids, put in a sandy substrate with a bit of gravel at the bottom of their aquarium.

4. Temperature

They are used to the warm temperatures of their homes in the wild. To mimic it, install a heater to help you maintain the water temperature at a range of (77-82)°F or (22-30)°C. They do not like sudden temperature changes, and an overly warm environment would make them restless, so closely monitor it.

5. PH

You should maintain a mildly acidic PH range of 7.0 to 8.5, and the water hardness has to be a range of medium-hard to extremely hard.

6. Lightning

They come from murky-looking waters with plants covering a large part of their surface. You would need the aquarium dim or near dark, or the shy cichlids would always hide. You can use a blanket of floating aquarium plants like hornworts to block off most aquarium lights.

7. Jack Dempsey Tank size

The Jack Dempsey fish love to have their space, so a big tank of about 48 inches is ideal for a juvenile, but a full-grown jack Dempsey fish would require up to a 55-gallon aquarium.

Remember, the bigger space, the less likely they have confrontational squabbles with other fishes. You would think a small tank would cause them to fight with only other fish types, but no, they are likely to lash out on co-specific, even their mate.

Tank Mates

Jack Dempsey fish tank mates should not be small-sized fishes or fry as they would prey on them. Their temperaments can make it challenging to find ideal tank mates for them because you want your community aquarium to flourish. Keep them with fishes with a comparable temper. They will live with other fishes if the tank has dividers or landmarks to help mark their territory.

Some good tank mate suggestions for the Jack Dempsey fish include:

When all options seem overwhelming to try, co-specifics are the way to go. Put other jack Dempsey into the tank as they have the highest chance of survival. However, do not put too many male Jack Dempsey together, as it can go wrong so fast.

Some Incompatible tank mate suggestions include;

  • Fishes that can fit into their mouths like tetras
  • Fishes that are too calm or peaceful and cannot hold their own in a fight.
  • The Jack Dempsey cichlids view invertebrates as a food source, so do not put shrimps or snails in their tank, except you are trying to feed your pet.


1. Picking Mates

The Jack Dempsey cichlids would pick a mate from the co-specific female in the tank. It is ideal to put them together early to mature and pair for it helps them get along better. Then, when they are ready, separate them from other fishes and put them in a breeding tank. They both would darken their coloration to show they are prepared to mate.

Remember, the couple does not like other mature fish around them; they will react extremely and may even kill to make that point. So only put them together in a breeding tank when the female is ready to spawn, or the male would chase and harass the female.

2. Tank Conditions for Breeding

The Jack Dempsey fish breeding rates have a higher probability when the tank mimics their natural habitat. They like to breed close to hilly rivers, for they have a sturdy platform for the female to lay their eggs. You can place a cave-like decor like a pot to simulate a hill. It is crucial to create an ideal environment for that number of fry.

A known breeding trigger is warmer water temperature; it causes mature fishes of 6-12 months to want to mate. The female Jack Dempsey is oviparous; she lays on surfaces while the male fertilizes them. They clean the laying surface before breeding. The cichlids develop a protective instinct as soon as the eggs hatch after three days.

The female lays often and would release up to hundred eggs every spawning period. The parents would burrow one or more pits in the substrate or use plants or aquarium pots and transfer their juveniles. They watch over them aggressively against any predatory tank mates.

4. After Breeding

The fry would begin to swim around the tank after ten days and eat nauplii, brine shrimps, or bits of food. The parent would provide food for the fry while they are in the pit as they can not fend for themselves. The male would occasionally fight his mate, so be observant and remove her from the tank if necessary. Their fights can be about the male being overzealous with his fry guard duties or making the female nervous.

In a highly stressful environmental condition, the parent would begin to eat their young. So keep them in separate tanks or big tanks for one and half a month to about three months so the female can rest, for it helps reduce their spawning frequency.


A wild Jack Dempsey fish diet is primarily carnivorous. They eat shrimps, insects like crickets, crustaceans, fishes, and worms. But a tank-bred jack Dempsey would eat almost anything you feed it, including other fish in the tank. They also enjoy flakes, dried food like worms and shrimps, pellets, and other live meals like fruit flies and grasshoppers.

Do not feed them poultry and beef as they have high fatty contents and can kill them. They would occasionally eat the aquarium plants, lettuce, and cucumber. Feed them twice daily, and they would not bother if their food sinks or float. Remove leftover to prevent decay which can increase ammonia in the aquarium water.


  • Jack dempsey fish or rocio octofasciataThe Jack Dempsey is an aggressive cichlid.
  • The Jack Dempsey species have different attractive color variants like blue and green.
  • Their scales and fins have an iridescence appearance like sparkling specks.
  • The juvenile jack Dempsey has a pale color and up to ten or eleven stripes.
  • An ideal tank mate for the Jack Dempsey fish are other cichlids, fast-growing fishes, or other aggressive species.
  • They eat aquarium plants, vegetables, live food, and frozen dry food.
  • They change color to almost black when they are ready to reproduce.
  • They are protective of their young but would eat their young if they feel threatened.

The Jack Dempsey can be a handful for a beginner fish-keeper because of its volatile nature. However, they are beautiful; they spawn without extra triggers and eat almost anything. You should consider expanding your community aquarium by getting yourself this pet fish as they could be with you for a long number of years.

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