Everything You Need To Know About Jack Dempsey Fish

jack dempsey fish

Jack Dempsey fish – when one finds out that the fish is named after a famous American professional boxer, the first impression is of a fierce and aggressive fish. This is exactly what the fish is known for.

Due to its reputation for being aggressive, it is not the perfect match for every tank keeper. 

If you want to add a Jack Dempsey to your tank, you have to be aware of things like:

  • What to feed a Jack Dempsey fish? 
  • How to set up a tank? 
  • Compatibility
  • Care level
  • Breeding 
  • Common diseases and causes etc. 

This article is aimed at providing you with all the information you need to know about a Jack Dempsey fish. It will serve as a comprehensive cheat sheet that will help you understand everything you should be aware of.

The people who are absolute beginner level fish keepers and are interested in opting for a Jack Dempsey can go through this guide to find out whether they can take on the responsibility of this fish or not. 


There is plenty of freshwater fish that have been named after humans. The case with Jack Dempsey fish is quite similar. Naturally, the fish belong to the regions of Mexico, Belize, Honduras and Guatemala. A large population of the fish can also be found in Asia, the United States and Australia. 

The appearance of these fish is truly stunning and attractive. Both the shape as well as the colors of the fish are unique. While most of the freshwater fish are taller, the Jack Dempsey fish is longer. Their tails are round and prominent, and both the dorsal and anal fins are also comparatively large. 

The color combination and shades of the fish are truly impressive. The base color of the fish is a dark shade of purple-grey. The scales of the fish spread over the body of the fish and are golden and bluish in color.

This combination gives the fish an ombre and shaded appearance making it stand out amongst any group of fish. 

The eyes are surrounded by two dark-colored bands. You may notice a change in the fish’s color based on different conditions. But a healthy fish is extremely attractive with the colors displayed in full swing and vibrancy. 

Overall, the fish have a shiny appearance as the spots reflect light. The strong facial expressions and large size of around twelve inches give the fish an overall intimidating look which is why it is named after a renowned American boxer. 

In terms of size, the male Jack Dempsey fish can grow larger as compared to the females. The males, in the wild, will easily be around twelve inches in length, whereas the females can be around ten inches in length.

But in captivity, the males can reach the maximum size of ten inches whereas the females will grow up to eight inches in length. 


The Jack Dempsey fish is notorious for its aggressive nature. Therefore, it is also known as the “Beautiful Beast” since it is a fish that looks extremely attractive but will not hold back from showing aggression when needed.

It is an extremely territorial fish that does not like to share its space. Therefore, it is best it is kept in a tank all by itself. 

Other than tank mates and their temperament, there are several other factors that can ignite the Beautiful Beast.

If you make the mistake of adding the fish in a tank that is not spacious enough for the fish to grow to its full potential or lacks space for the fish to swim around peacefully, you will see chaos and anger in the fish. 

The Jack Dempsey fish tends to get more and more aggressive as it grows. The juvenile Jack Dempsey’s are quite peaceful, but as they reach adulthood and maturity, they start acquiring the aggression they are very well known for.

You will notice that the fish will get significantly darker in color when triggered. It is a sign that Jack Dempsey has lost its temper, and it will be foolish for anyone to try and mess with it. 


The Jack Dempsey fish is an omnivorous fish which means it can be fed both proteins as well as plant-based diets. Despite being omnivorous, their favorite food remains meat.

They can be fed a wide range of food including pellets, flakes, shrimps, worms, and shellfish, etc. Frozen food is also a favorite.

Make sure that you add live food to the tank every once in a while. You will see that the fish will love chasing it around and feeding on it. Live food is not only a great source of entertainment for both the fish as well as the tank keeper to watch, but it also keeps the fish active and energetic. 

It is best that you maintain a proper balance when it comes to feeding a Jack Dempsey fish. Include meat as well as vegetables to ensure that the fish’s nutritional needs are met properly.

Vegetables like cabbages, lettuce, and carrots are highly recommended. Make sure that the vegetables are chopped as finely as possible as it will make it easier for the fish to consume them. 

Although the Jack Dempsey fish can be fed herbivorous diet, it will never eat the plants inside the tank. Therefore, make sure that some plant-based food is incorporated in the fish’s diet by feeding it vegetables and pellets. 

The most common query tank owners put forward is how often do you feed Jack Dempsey fish?

Tank owners need to be extremely vigilant when feeding their Jack Dempsey fish. In fact, the most common mistake people tend to make is to overfeed the fish. Overfeeding the fish can lead to a lot of health issues and also cause complications for the fish’s digestive system. 

Keep an eye on the fish while feeding. Add the food to the tank in small portions and only add the amount that the fish can easily consume within three minutes. Feed the fish small portions of food, and the frequency of feeding should be two to three times per day.

Each fish is different and thus has different feeding needs. The best approach is to observe your Jack Dempsey and assess which time, quantity and frequency of feeding suit your fish the best. 

Care Guide

The Jack Dempsey fish has an intermediate care level, but even beginner level tank keepers can get accustomed to taking care of this fish and add it to their tanks with a little bit of extra effort.

The fish is not very demanding or particular when it comes to tank conditions and food; therefore, it is simple to care for, and you can easily get around to its requirements and demands. 

When you plan on setting up a tank for the Jack Dempsey fish, try and recreate their natural habitat to the best of your ability. If you care for your fish properly, it can easily live for up to ten to fourteen years.

They come from slow-moving freshwater and tropical climate conditions. They have low lighting requirements but prefer acidic water. 

  • Tank Size

People often wonder what size tank a Jack Dempsey fish need. These are bigger fish that require more room and space. If you plan on keeping one fish, a 55-gallon tank should suffice. For a pair, a tank size of 100 gallons is recommended. 

These are the bare minimum tank size requirements. Feel free to opt for a larger tank. As already discussed, adding them to a tank that is too small can lead to aggression. The Jack Dempsey fish loves to swim around, therefore ensure that it has ample space to be able to do so. 

  • Filtration

Fish that are bigger in size are no doubt more attractive. But at the same time, bear in mind that they also come with a larger biowaste. The Jack Dempsey fish is also one such specie that will produce a lot of waste inside the tank. 

If the tank is not filtered properly, this waste will start accumulating and eventually breaking down into ammonia in the tank, thus raising the nitrate levels.

Make sure that you add a large capacity filter to the tank so the fish waste can be removed and the tank’s hygiene and cleanliness can be maintained.

To summarize, the tank for Jack Dempsey fish requires a large filter that can clean the tank and prevent ammonia buildup inside the tank. 

  • Heating

Naturally, the Jack Dempsey fish comes from a very warm region. Therefore, a heater must be added to their tank to maintain a comfortable temperature.

Make sure that you invest in a heater that has the capacity to heat the water in your tank and maintain the temperature. The ideal temperature range for Jack Dempsey fish is between 72-86 degrees Fahrenheit. The pH should be between 6-7 with a water hardness level of 9-20 dGH. 

  • Substrate

There is a wide range of substrates for one to choose from. However, if you are setting up a tank for Jack Dempsey fish, make sure you opt for either sand or gravel substrate. Jack Dempsey fish love to dig around in the substrate.

If you add a substrate that is too grainy or harsh, it can end up causing injury to your fish. Moreover, these substrates are lighter in color, so they extenuate and bring out the colors of the fish, making the Jack Dempsey prominent and highlighted. 

  • Plants

Almost all cichlids love to share their tanks with plants and in the case with the Jack Dempsey fish is no different. But bear in mind that the Jack Dempsey fish loves to dig around in the substrate; therefore, it is likely that it will end up uprooting the plants. 

Therefore, the plants that have to be planted in the substrate of the tank are not the ideal choice for a Jack Dempsey fish tank. Do add some plants to the tank but try and opt for floating plants.

These plants do not have their roots in the substrate of the tank and float freely on the surface of the water. Thus, these plants cannot be disturbed by the constant digging of the substrate by the Jack Dempsey fish. 

Hornwort is the ideal choice for a tank with Jack Dempsey in it. 

  • Décor Items

Jack Dempsey fish like to have free space inside the tank to swim around peacefully. But it is a good idea to add some décor to the tank.

The fish will not only use these items to mark their territory but will also use them to hide when intimidated (which is quite rare considering the Jack Dempsey fish is the one who will intimidate other tank mates!)

Compatibility and Tank Mates

People often inquire about whether Jack Dempsey fish can be added to a community tank. These fish are known for their aggression; therefore, adding them to a community tank will not be a good idea.

Plus, as they grow older, they start showing their territorial nature, thus making them extremely specific about their space.

Once they have marked their territory, you will often find them guarding their space and threatening other fish if they dare to make their way into Jack Dempsey’s empire. 

Two mated Jack Dempsey fish can be placed together in a tank. However, make sure that the tank is large enough to easily accommodate both of the fish, so the fish do not end up getting into a fight every now and then.

Even in a large tank, it is likely for the pair to have a face-off, but more space reduces the chances of them getting aggressive towards one another. 

However, it is important to note that the breeding pair will never share their tank. If any other fish is added to the tank with the mated pair, the pair will fight it and ensure that the fish cannot live in the tank peacefully even for a minute. 

Make sure that the pair of Jack Dempsey you are keeping together are of the opposite sex. If you add two males to the same tank, they will fight till either one or both of them are dead.

It can be rightfully stated that two male Jack Dempsey fish in a tank is synonymous with trouble, chaos, and a deadly face-off. 

Do you understand why they are named after a popular American boxer now? 

Never make the mistake of adding Jack Dempsey fish with small-sized or peaceful fish.

If you plan to create a community of fish along with Jack Dempsey’s, make sure they are housed with similar large size fish that share an aggressive nature. Some ideal tank mates for these fish include the Green Terrors, Severums, or Firemouth fish. 

Firemouth Cichlid
Firemouth Ciclid

Since all the fish are territorial and large in size, therefore, you will require a very big tank to house them all peacefully.

If you are a beginner level tank keeper or a person who cannot take responsibility for the care and maintenance of such a large-sized tank, it is better you do not try to pull off keeping Jack Dempsey fish with any tank mates. 

Differentiating Between Sexes

Identifying male and female Jack Dempsey fish is important if you plan to create a mated pair and also if you want to breed them. Unlike some other cichlids, identifying the sexes of the Jack Dempsey fish is quite simple and straightforward. 

The male fish is an inch or two longer than the female fish. Other than this, the female Jack Dempsey fish has more bright and vibrant colors as compared to the male one.

The dorsal fins can also be used to identify the male and female fish. The female fish’s dorsal fin is smaller and a bit rounder as compared to that of a male. 

The spots on the body of the fish can also be used to identify gender. The female has fewer spots as compared to the male Jack Dempsey fish. And you will always find the male to be more aggressive and territorial as compared to the female fish. 

Breeding Jack Dempsey Fish

Before breeding, it is important to do some preparation and help the male and the female Jack Dempsey fish. It is ideal for the mating pair to be removed from the main tank and placed in a separate tank.

However, if this is not possible for you, the least you can do is to make use of an aquarium tank divider so the pair can be isolated from the rest of the fish. 

When selecting the pair, make sure that both the male and female get along well with one another. Although it is less likely for a pair of the opposite sex to get into a fight, it is still possible.

To prepare the pair for breeding, put them on a protein-rich diet. This should be continued for around three to four weeks. The temperature of the tank should also be lowered and maintained around twenty-eight degrees. 

The breeding tank should be set up in advance. It should be clean, and the parameters should be stable, so the pair does not have to encounter any type of issue or trouble. Ample hiding spaced using plants and décor should also be provided. 

In a single breeding session, the female Jack Dempsey fish will lay around five to eight hundred eggs. When ready to spawn, the female fish will move around the tank and dig in the substrate to find a suitable place for her to lay the eggs.

As soon as the female fish is done laying eggs, the male Jack Dempsey fish will make its way to the spot and fertilize the eggs. 

Unlike other fish that tend to become hostile towards the eggs and fry, the Jack Dempsey fish is quite considerate. As soon as the eggs have been fertilized, both the male and female get to work to protect the eggs.

The female will remain close by and watch over the eggs while the male Jack Dempsey fish will protect the territory and try and fight off any danger. 

It is so interesting to note that despite being aggressive, the Jack Dempsey fish are so concerned about their eggs. If the female finds that the male is lagging or is not doing his job properly, she will move close by and even get into a fight with him! 

If you notice too many fights in the tank, it is best to remove the male from the tank. The male Jack Dempsey fish is the one with the most aggression, and it may end up hurting or killing the female fish and even consuming the eggs if it gets too mad. 

The fertilized eggs will hatch and release fry into the water within three to six days. The fry will begin eating at around eight to ten days of age. The fry should be fed pulverized food that is easy to consume.

You may find the breeding pair chewing on the food and releasing it into the water after breaking it down into smaller pieces so the fry can easily feed on it. 

Make sure that the juveniles are cared for properly. The tank conditions should be strictly monitored and maintained. Special attention needs to be paid to the overall hygiene and cleanliness of the tank. The best way to do so is by scheduling 25% water changes per week. 

To control the population of the tank, the use of culling is highly recommended. 

Common Diseases and Causes

The Jack Dempsey fish is hardy and strong. Yet, it may come across some diseases if not cared for properly. The major causes of disease and illness in the fish is none-other than poor hygiene and either under or overfeeding. 

Keep a close eye on the fish in your tank, so you are aware of their temperament and activities. If you find that the fish is too lethargic or acting differently, it may be a sign of illness.

Another indication of the disease is the alteration of the physical features of the fish. Physical injury or marks on the body and the colors of the fish getting paler are some red flags that you should be aware of. 

The most common disease that Jack Dempsey fish fall prey to is the Hole In The Head Disease.

Fish with a weaker immune system are more likely to develop this disease. The bacteria Hexamita, poor water sanitation, and conditions, as well as a diet that lacks vitamins, causes this disease.

You will see small lesions emerging on the head of the Jack Dempsey fish along with the loss of appetite and overall lethargy. 

Skin Fluke is another disease that is quite common in Jack Dempsey fish. These are parasites that can attach themselves to the different parts of the fish’s body. As a result of this unwanted guest, you will see lesions on the fish’s body along with discoloration and excessive production of mucus.

The fish will also scratch its body against hard and rough surfaces like driftwood and rocks to get rid of the discomfort. Skin medication and antibiotics have to be prescribed to help the fish get back to health. 

Freshwater Itch is one disease that is common for almost all freshwater fish. This disease is also caused by a parasite and leads to the development of small white spots all over the Jack Dempsey fish’s body.

It can also lead to breathing issues, weight loss, and change in the fish’s swimming pattern. This disease can be treated via heat treatment and prescribed medicines. 

Is Jack Dempsey The Right Choice For My Tank? 

Jack Dempsey fish are a bit tricky. They are cichlids, but unlike the other fish that belong to this category, these fish require special care and attention. The biggest challenge associated with the Jack Dempsey fish is its aggressive and territorial nature paired with the large size. 

If you think you can add the Jack Dempsey fish to a community tank, you are wrong. Nor can this fish be added to an already setup tank. It has its own set of requirements and specifications that have to meet in order to keep it happy and healthy. 

Once you have set up the tank according to their requirements, they are fairly simple to care for. Feed them well and keep an eye on them to ensure they are not sick. But still, keeping Jack Dempsey fish is not for the fainthearted.

You will have to invest in a larger tank with the appropriate filtration and heating equipment. Caring for a large-sized tank, especially with Jack Dempsey’s inside is not simple. Therefore, these fish are not an ideal choice for beginner level tank keepers. 

However, if you have some experience with fishkeeping and are willing to take on a challenge, the Jack Dempsey fish will surely not let you down!

John Kilmerstone

I love keeping pet fish and receive a lot of joy and peace from watching these colorful creatures. Please visit this website and explore the wonderful world of pet fish. Discover how to care for and look after pet fish and amplify your satisfaction.

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