Jack Dempsey Fish: A Guide to Breeding, Diet & Behavior

The Jack Dempsey fish is one of the most popular and sought-after species in the aquarium hobby, which comes as no surprise.

These fish, also known as Rocio octofasciata, belong to the Cichlidae family.

This aggressive, large-bodied fish has a lot to offer any aquarist, including beauty, personality, and hostility. However, they, like any pets, require attention and adequate habitat.

I’ll tell you all you need to know about the Jack Dempsey fish in this blog post, including…

Jack Dempsey Fish Overview

Jack Dempsey Fish Overview

Family: Cichlidae
Origin: North America, South America
Temperament: Aggressive
Size: 10-15 inches
Minimum Tank Size: 55 – 80 gallons
Diet: Carnivore
Care: Intermediate
pH: 6.0 – 7.0
Alkalinity Levels: 9-20 dH
Temperature: 74°-85°F (23°-29°C)


Like other Cichlids, Jack Dempsey Fish are native to North America, South America, and Africa.

They are endemic to the Amazon River basin, which includes Peru, Brazil, and Columbia, where they reside in vegetation.

This contains flooded meadows or floodplains with plenty of shelter for them to hide in if necessary.

They’ve already established themselves in the warm waters of Australia and Thailand, where they’re known as the Mexican Blue Frontosa.


Jack Dempsey fish have a pugnacious appearance, with powerful facial features and a huge head and body, reminiscent to the 1920s fighter Jack Dempsey.

This fish has long, thin fins and a long, thin body. Males will have longer fins and be bigger. The male’s fin is longer and more pointed than the female’s fin.

They have a brown overall colour with black dots on the top of their bodies that get larger around their tail fin region.

This fish’s name comes from the vivid yellow hues that run the length of its fins while remaining darker at the ends.

Golds, blues, and pinks are the most common hues, and their color will vary as they age.

Younger fish have a light green tint with green spots at first. Their tint turns to vivid green-blue specks as they age.

Color can vary for a variety of reasons, not just age. When they are anxious or mating, they turn a lighter hue.

The electric blue color scheme Since the breed’s initial name was “Jack Dempsey,” a popular variant of this species called “Jack Dempsey” has risen in popularity.

This variety is less aggressive and smaller than the ordinary Jack Dempsey.

Jack Dempsey Fish Size

Male Jack Dempsey fish grow to be roughly 10-15 inches long, while females are a little shorter.

Typical Behavior

Jack Dempseys are noted for being territorial and aggressive.

They frequently battle with other fish of the same species and will kill any fish that threatens their food or territory.

As a result, many individuals are turned off by them, and we would not suggest them to novices.

Because it’s more difficult for them to single out and prey on lone fish in densely packed aquariums, they’re less aggressive.

How Long Do They Live?

The life expectancy of a Jack Dempsey fish is 10 to 15 years.

Electric Blue Jack Dempsey

Electric Blue Jack Dempsey

A mutant version of the common Jack Dempsey.

It has all of the same requirements and temperament as its more common cousins, but is less aggressive.

It’s worth noting that they’re quite scarce in their native environment, making them even more desirable to aquarium owners!

They also have vivid yellow spots and stripes around their fins, which distinguish them from other varieties of jack dempsey fish.

Females of the Electric Blue may grow up to 15 inches in length, while males average 12-13 inches.

They require an aquarium with a capacity of at least 100 gallons, so make sure you have enough space for them before adding any water, as these fish may grow rather large.

Habitat and Tank Conditions

Tank Setup

The water temperature should be kept between 74°-85° degrees Fahrenheit (23-29 Celsius).

pH levels should range from around 6 to 7 and the hardness level below 100 ppm.

  • Temperature: 74°-85°F (23°-29°C)
  • Ammonia/Nitrite: 0
  • Nitrate: <40 ppm
  • pH: 6.0-7.0
  • GH: 3-8 dGH (50-133 ppm)
  • KH: 4-6 dGH (72-107 ppm)

What Size Aquarium Do They Need?

For a single Dempsey, a 55 gallon fish tank is recommended as a minimal minimum.

If you have the option, always go larger. A larger tank, such as an 80 gallon tank, is always preferable.



The importance of filtration in any aquarium cannot be overstated. Dempsey Fish are large, messy eaters who leave a lot of trash behind.

Some people recommend going with a larger filtration system, but the best suggestion is to have adequate flow for the size of your tank.

That means if you have a 55 gallon tank, ensure sure the filtration rate (gph) is sufficient for the filter’s gallons per hour rating (s).

Canister or sump tanks are the ideal filters to utilize since they give superior water quality and oxygenation without taking up too much space in your home.

Filtration will help to minimize nitrates, which can accumulate over time.

It also offers clean, wholesome water, which aids in the promotion of breeding behaviors and the reduction of stress in fish populations.


Because Jack Dempsey fish dwell in the warm seas of South America and Africa in the wild, it’s critical to replicate these conditions in their aquarium.

It’s usually a good idea to get a larger heater than you think you’ll need because the fish will be more comfortable and less likely to die of shock.

Make sure your heater is set up far enough away from any sharp pebbles or other items in the tank, since this might cause damage over time.

Plants, Substrate and Decor

If you, like me, enjoy a wide variety of aquarium plants, the Jack Dempsey fish is not the species for you.

Because these fish are known to be hostile towards plants, you should avoid any stem plants, especially those with long leaves.

It’s conceivable that you’ll receive some Dempsey fish that aren’t as destructive, but it’s tough to say because each one is unique.


In terms of substrate, you may use fine gravel or sand – whatever you choose – but make sure it’s dark in color so it doesn’t show through the coloration of your fish.

It’s also a good idea to go with an inert substrate. Substrates labeled “cichlid sand” should be avoided.

A planted dirt substrate is not a suitable choice for Dempsey’s since they enjoy digging and would break it up.


Additionally, because they are territorial species by nature, you’ll need some pebbles and/or wood to adorn your tank.

Large rocks or driftwood fragments that they may hide under make great hiding places once they’ve completed developing.


It’s preferable to emulate the natural appearance of deep water when it comes to illumination, and LED is a fantastic option.

LED lights last far longer and consume much less energy than incandescent bulbs, making them an excellent choice for aquarium lighting. LEDs also give an aquarium a more realistic appearance.

Tank Mates

It’s crucial to match the kind of fish in a tank correctly, but because Jack Dempsey fish are notoriously aggressive, this can be a challenging chore.

Other species cannot be kept in the same tank as jack dempsey fish because they will attack and kill them.

The only exceptions are a very aggressive “alpha” kind of fish that is larger than your Jack Dempsey, or a much smaller beta-type species that won’t cause the Jack Dempsey any territorial aggressiveness.

Here are a few excellent examples:

  • Firemouth Cichlids
  • Blue Acara
  • Angelfish
  • Plecos
  • Clown loaches
  • Silver Dollars
  • Convict Cichlids

Can You Keep Jack Dempsey Fish Together?

The ideal approach for novices is to maintain Jack Dempsey’s in a species-only aquarium. Other species could be more difficult to keep alive.

It’s ideal to have one male per tank, especially since males don’t get along with each other.

Common Illnesses

Jack Dempsey Fish, like any other species, can contract common ailments. But

Knowing the most prevalent ailments might aid in the recovery of your fish.

The most prevalent ailment is “hole-in-the-head” sickness, which causes a hole in Jack Dempsey Fish’s face. Other ailments caused by bad water conditions include ich and fin rot.

To protect infections from hurting Jack Dempsey’s, ensure that their environment is well-maintained by performing frequent water changes and avoiding overcrowding or overfeeding.

Use aquarium salt together with other drugs as suggested on the packaging to treat an unwell Jack Dempsey until they recover their health.

Remember that not all treatments are effective in all situations, so get expert advice before making any decisions that might jeopardize your fish’s life!

Diet and Feeding

In the wild, the Jack Dempsey will eat everything that fits in its mouth, including small fish, worms, insects, and crustaceans.

They don’t have a picky palate and will consume frozen, fresh, or live foods.

Here are a few dishes that they will enjoy:

  • Bloodworms
  • Fresh or frozen shrimp
  • Fruit flies
  • Brine shrimp
  • Crickets
  • Grasshoppers

How often should I feed my Jack Dempsey?

Adults should be fed one or two times per day, while young Dempsey should be fed two to three times per day.

To avoid decomposition, any uneaten leftovers should be removed from the tank within a few minutes.


When they’re ready to mate, Jack Dempsey’s color will deepen.

The water must be clean and within the conditions indicated above before spawning may commence.

A reliable trigger is a temperature of 84°F or greater.

Then you should feed them live food, or you may imitate breeding by giving them live worms.

When they’re ready to reproduce, start giving them a spawning mop made of java moss, cotton wool, or pantyhose tied in knots with black thread.

The male will wrap himself around the spawn location and shift it so that any eggs deposited will fall into this region, which he will fertilize. It is possible to generate up to 500 eggs.

There may be no movement at first, but after three days, small fry will develop all over the place, including on plants and pebbles.

They develop swiftly after birth, frequently doubling in size every week over the following four months until they reach two inches in length (four cm) at six months.


Owing to their incredibly aggressive temperament, Jack Dempsey fish are a popular option due to their fascinating qualities. However, they may not be the greatest species for beginners.

Keep in mind that this fish does not get along with other species and is best kept together.

Maintain in mind that males do not get along well, so keep one male per tank.

Do you have any Jack Dempsey fish in your aquarium? What kind of experience do you have with this species? Please let us know in the comments section below.