Jack Dempsey Fish Care Guide: 5 Must Read Facts

The Jack Dempsey Fish is a shining and shimmering Central American Cichlid.

Without a doubt they are one of the most popular freshwater fish in the world.

While they may be beautiful, they are also quite a handful. Their aggressive and territorial temperament can be difficult for beginners to tame.

Are you up for the challenge to keep a Jack Dempsey Fish?

Keep reading to learn everything you need to know about taming this ferocious little fighter…

Jack Dempsey Fish

Jack Dempsey Fish
Other Common Names: Mexican Blue Frontosa, Electric Blue
Scientific Name: Rocio octofasciata
Family Name: Cichlidae
Distribution: Central America
Size: 8-12 inches
Color: Green, blue, purple, gold
Care Level: Intermediate to Expert
Temperament: Aggressive
Lifespan: 8-15 years
Minimum Tank Size: 80 gallons
Tank Mate Compatibility: South American Cichlids and other medium to large fish

Jack Dempsey Fish Overview

Jack Dempsey Fish Swimming

The Jack Dempsey Fish (Rocio octofasciata) is a tropical freshwater fish from the Cichlidae family.

They are native to Central America, but now a few invasive populations have made their way into the United States, Australia, Thailand, and even Russia.

Their name comes from William Harrison Jack Dempsey who was a heavyweight boxing champion in the 1920s. This fish’s fighting spirit certainly brings to mind a boxing champ! For such an aggressive fish, they are surprisingly community friendly. Lots of people have had success keeping this fish with South American Cichlids.

Their flashy appearance is what often attracts inexperienced aquarists.

Blue is one of their most mesmerizing and most sought after color forms.

You can find this fish at most pet stores and online aquarium suppliers. While some stores will sell them for as low as $5, the average price for one is about $15.

Key Facts:

  • Experience Required: Cichlid keeping, aggressive species.
  • Nicknames: Mexican Blue Frontosa, Electric Blue.
  • Color Forms: Green, blue, gold, purple.
  • Size: 8-12 inches.
  • Tank Size: Minimum 80+ gallon.
  • Tank Temperature: 74°F to 86°F.

Pros and Cons

  • Lots of different colors and patterns.
  • Will not eat your live plants.
  • Thrives in a Cichlid community tank.
  • Have a long expected lifespan.
  • Aggression can be hard to manage.
  • Not safe for tanks with small fish or invertebrates.
  • May turn on each other during mating.
  • Likely to have some conflicts with their tank mates.

Jack Dempsey Appearance

Jack Dempsey In Aquarium

The Jack Dempsey Fish is shaped like a bullet with stern and ferocious facial features.

They always look ready to start a fight!

Their long dorsal fin reaches all the way back to the caudal fin, which is shaped like a fan and can be rounded or pointed at the tips.

Jack Dempseys also have a pair of pectoral fins, a pelvic fin, and a long anal fin. This makes for a grand total of 6 fins.

You can look at the fins to tell the difference between males and females. The male’s dorsal and anal fins are pointed at the end, whereas the female’s are rounded. Males also have a general thicker build yet tend to be more streamlined shape.

Their most notable feature is their color.

They have iridescent spots that can be any color from blue to green to gold. Their spots shimmer in the light no matter where they go. Their sparkle is why so many people love them, in spite of their challenges!

Jack Dempsey Fish Size

While they do not grow as large as the Oscar, this is definitely one of the larger Cichlid species around.

Females reach a maximum of 8-10 inches.

Males top off between 10-12 inches.

Common Color Varieties

Electric Blue Jack Dempsey

Electric Blue usually refers to the Electric Blue Acara, an African Cichlid. However the Jack Dempsey has its own Electric Blue color form. An Electric Blue Jack is neon blue, with black spots and markings over their body and fins. This color is the result of artificial selection and does not occur in nature.

Black Blue Jack Dempsey

This is another spectacular blue color form, but it comes in a different shade than the Electric Blue.

Their body is usually black or dark grey and they have a sprinkling of iridescent blue or purple spots. This color can occur in nature, but it is very rare.

Other Color Varieties:

Some of the many beautiful colors that you can choose from include:

Green: This is the most common color variety. Shimmering green spots decorate a dark grey, black, or brown base color.

Blue: A non-electric blue fish features royal blue spots over a black or black banded body.

Electric Blue: This completely man made color form features a neon blue base color with black spots and markings.

Gold: A gold Jack will have a golden orange body with blue or green spots, or a dark brown body with shimmery gold spots.

Purple: This one has a dark grey, black, or black banded body with a sprinkling of purple spots.

Mixed: Mixed varieties can sport any combination of the typical colors for the species.

5 Fun Facts About Jack Dempsey Fish

  1. Most aquarium Cichlids come from Africa or South America, but the Jack Dempsey is one of the rare ones that is native to Central America.
  2. They have now established populations in Hawaii, Florida, and even South Dakota.
  3. The fish can change colors based on their mood, tank conditions, or diet. Sudden color changes can mean they are not feeling well or that they are not getting the proper nutrition.
  4. Just like other Cichlid species they take care of their young. Both parents guard the eggs and care for the fry until they reach the juvenile stage.
  5. Although they are a Central American species, they can live with Cichlids from South America due to their similar water conditions and care requirements.

Breeding Jack Dempsey Fish

These substrate spawners are used to breeding in caves in the wild.

If you want to breed them you must first create a cave out of a flower pot, PVC shelter, or a cluster of rocks.

A paired male and female will eventually breed without any help from you.

Once a male is ready to breed his colors become darker and flashier.

He will charge the female several times in an attempt to get her attention. If a female rejects a male then he will continue to charge her until she dies. So you should remove any females that are unwilling to spawn.

A mated pair will viciously attack all of your other fish in the tank, so make sure to move them to the breeding tank as soon as they have paired off.

Your pair will get to work building a nest by digging out a pit in the substrate.

Once she is ready to mate the female can lay up to 800 eggs at a time.

Both parents take care of the eggs and the larvae, and will attack anyone who disturbs them. Unfortunately, this includes your fingers when you are trying to feed them!

For the most part, the larvae and the fry will be fed by the parents. However, you still need to provide them with the right foods to eat. Infusoria, larval brine shrimp, and commercial fry food can be used to feed the fry.

The parents will chew the food and regurgitate it for them to eat.

You can move the parents back to the main tank once the fry reach the juvenile stage. Your juveniles will reach full maturity after about 6 months.

History and First Sighting

Electric Blue Jack Dempsey

They were first discovered by Regan in 1903.

Back then they were known by their scientific name (Rocio octofasciata) however around 20 years later they were nicknamed Jack Dempsey Fish.

Throughout the 20th century this fish and other Cichlid species were used in freshwater fish studies. Scientists were particularly interested in their territorial behavior and parental abilities.

They first entered the pet trade during the 1950s in East Asia.

Their popularity rose in the western aquarium trade throughout the 1980s and 1990s.

By the year 2000 they became a staple in the freshwater aquarium hobby.

Because of their success in the aquarium hobby they have established wild populations in Thailand, Australia, Russia, and three US states.

Natural Habitat and Tank Conditions

Black and White Jack Dempsey

In the wild this fish lives in wetland pools and slow moving channels with only a moderate current.

They tend to live in areas where a lot of algae is allowed to grow.

Outside of their natural range they live in irrigation ditches and other man made bodies of water, especially those that are heated by an artificial heat source.

They will stay near the bottom of the water column where the light is low and where water temperatures can go all the way up to 86°F.

Aquarium Set Up

You will need at least an 80 gallon aquarium so your Jack can swim around without bumping into anything, including other fish.

The water should be heated to a temperature between 74-86°F and you will need a heater that is powerful enough to heat at least 80 gallons of water. The pH should be between 6.0-8.0, and the hardness can be anywhere from 9-20 dGH. As a euryhaline species, they can tolerate higher salinities.

A high power external or canister filter is the best kind for this aquarium. Just make sure to keep the flow low to moderate.

You will also need to cover your tank with a hood to stop them from jumping out.

Now for substrate you should use a fine to medium grained sand or gravel.

You must decorate the tank with plenty of hidey holes and crevices for your fish to hide out in. Flower pots filled with gravel will make your fish feel right at home. You can also scatter boulders, driftwood, and bogwood around the tank to provide a little bit of extra shelter.

Algae is plentiful in the fish’s natural habitat so you should allow a fair bit of algae growth in your tank as well. You can use Marimo Moss Balls.

Plants are not necessary and your fish will likely dig them up.

If you do want to add some greenery then you can use floating plants like Hornwort and Duckweed.

Just remember, do not add your Jack Dempsey to the tank until it is cycled. Read How To Cycle A Fish Tank for more guidance.

Tank Parameter Requirement
Minimum Tank Size 80 Gallons
Tank Type Freshwater
Temperature 74-86°F
pH 6.0-8.0
Hardness 9 to 20 dGH
Flow Light
Substrate Fine to medium sand or gravel

What Size Aquarium Do They Need?

Juveniles can be kept in a 55 gallon tank until they reach full maturity.

An adult Jack Dempsey needs at least an 80 gallon aquarium. For each additional Jack Dempsey in the tank you should add 20 gallons.

Tank Mates

Jack Dempsey Close Up

Finding the right tank mates for this ferocious fish can be tricky.

Because they are known for bullying other fish, their tank mates must be able to fight back when needed.

In the wild they live with many different species of Tetras and Killifish, as well as the Mayan Cichlid and some South American Cichlids.

Within your aquarium their best tank mates are medium to large sized South American Cichlids. Convict Cichlids, Green Terrors, Firemouths, and even Oscars can all be kept with Jack Dempseys.

Freshwater Angelfish are safe as well. They are just peaceful enough to avoid causing trouble but still fierce enough to fight back.

Outside of the Cichlidae family, large Pleco catfish make a great tank mate for this fish.

Other good tank mates include the Clown Loach, Silver Dollar, Giant Danio, and larger sized Rainbowfish.

You should avoid keeping peaceful fish of any size with a boisterous Jack. This means no Gouramis, Dojo or Kuhli Loaches, or peaceful Cichlids like the Discus. Any small fish such as Tetras, Bristlenose Plecos, and Rasboras should also be avoided for the same reason.

You should also not introduce any invertebrates either because this fish will eat them.

Finally, avoid any African Cichlid. African Cichlids may carry diseases and parasites that can spread to a Cichlid from another region.

Keeping Jack Dempseys Together

If you are new to this species then you should not keep Jack Dempsey Fish in a community tank.

Instead you can keep this fish in a species only tank.

You can keep a few Jack Dempseys together so long as the group is mostly female. One male for every 3 or 4 females is a good rule to follow.

Keeping too many territorial Cichlids together can turn your aquarium into a boxing arena. It is vital to make sure that each Cichlid has enough space (20 gallons each) to go along without disturbing the others.

Jack Dempsey Care Guide

A Jack Dempsey Fish With Plants

This is not a good pick for a first time fish keeper.

However they can be a good pick for experienced fish keepers who are looking to keep a member of the Cichlidae family for the first time.

A Jack Dempsey’s colors reflect the quality of their care. Paleness, dullness, or other forms of discoloration are all signs that something is wrong.

Your biggest problem will be dealing with their aggressive and rambunctious personality (more on this later).

You might see visible wounds on a fish that has been in a fight. These will heal on their own and are not usually a cause for concern. Seek medical attention if a wound is not healing or if your fish is hiding or behaving erratically.

Once you get this under control there are not too many care issues to be concerned about.

This species is susceptible to ich just like most other fish.

Ich is very easy to spot on such a colorful fish – just be on the lookout for a sprinkling of little white spots.

Also because their fins are very wide they are susceptible to fin rot.

So 25% water changes are needed every 2 weeks.


This fish is an omnivore in the wild.

However most of their nutrition comes from live prey. They eat insects, arachnids, larvae, small crustaceans, and small fish.

In the aquarium they will eat just about anything you give them.

But their favorite is live prey with a high protein content.

You can feed them brine shrimp and frozen feeder shrimp like Grass Shrimp.

Bloodworms, mealworms, and tubifex worms make a tasty snack for your Jack. If your tank has a problem with nuisance worms then your Jack Dempsey Fish will have it cleaned up in no time!

They will also clear away a bit of algae in your tank.

Grasshoppers, crickets, and beetles from a reptile shop make a great high protein treat for your fish.

Any flake or pellet foods should be high in protein and specially formulated for Cichlids.

You should feed them twice a day.Once just after sunrise and again in the hours after dusk. Your fish must be able to eat whatever you give them in under 2 minutes.

A Jack Dempsey Fish


Just like most Cichlids, the Jack Dempsey is very territorial.

They will go after any other fish that swims into their territory.

Fighting Cichlids lock lips as if they are kissing. As a warning they will charge or rush an intruder with their mouth wide open.

However despite their aggression they are surprisingly shy and asocial.

For the most part they will stay at the bottom levels of the tank.

You will notice they spend most of their time hiding away during the day and will not make an attempt to interact with your other fish.

When they are active you will find them digging.

Should You Keep The Jack Dempsey Fish? (Summary)

The Jack Dempsey Fish is definitely not for everyone.

Their aggressive nature makes them difficult to keep for inexperienced fishkeepers.

Anyone looking to keep one should have prior experience with other aggressive fish.

Respect this fish, and they will respect you in return. If you can work with all of their quirks then they make a lovely addition to a freshwater tank. The most important thing to remember is to give them enough space. This will keep the number of underwater boxing matches to a minimum.

While the Jack Dempsey Fish may be a challenge to keep, they have certainly earned their spot as one of the most popular freshwater fish around.

These very active fish can be quite fun to watch. When they flash their colors, it is very hard to take your eye off of them.

There are many different colors and patterns to choose from and all kinds of ways to make this fish feel welcome in your tank.

Which color is your favorite? Let us know in the comments below…