April 22

Proven Jack Dempsey Fish Care Guide To Feeding, Size, Breeding and Tank Parameters


Jack Dempsey Fish

It is not very often you will come across a freshwater fish that bears a human name, but if there is an Oscar, then the Jack Dempsey fish should not be a strange one. Known by the biological appellation, Rocio octofasciata, the fish gets its name for the fierce look and aggressive behavior – which was characteristic of popular American boxer of the ’20s, William Jack Dempsey Harrison – it portrays.

The Jack Dempsey fish is a cichlid that is widely distributed in Central and North American waters; they particularly found in abundance in countries like Guatemala, Belize, Honduras, and Mexico. They are seen inhabiting slow-moving water and can grow up to 25 cm long in the wild.


The very first thing that will appeal to you upon sighting the Jack Dempsey fish is its striking pearlescent coloration. It is very attractive, and full of colors; the skin is dark purple-grey and has iridescent scales of blue gold and green spread all over the body, the fins inclusive.

Jack Dempsey’s fish size can be anywhere between 14 to 26 cms long when kept in the right size aquarium and given the right diet. 

It also has dark-colored bands appearing between the two eyes. Additionally, multiple stripes run along the fish’s body, and there is a black band on the caudal fin. It should be noted that the color of the Jack Dempsey fish may vary under certain conditions– this will be discussed much later in the article.

About the body outline; Jack Dempsey fish has an oval body that is laterally compressed. They have a pretty long dorsal fin and an anal fin which are both pointed and have red markings on the edges while the caudal fin is shaped like a fan.


One may choose to call the Jack Dempsey fish ‘a beautiful beast’ when considering its behavioral traits. This is because of its aggressive tendencies towards tank mates –this fish does not always share its space peaceably with others; it will not tolerate intrusion. In essence, it is quite territorial; hence, it is best to leave them alone in the tank.

But besides the sight of other tank mates triggering a hostile reaction from Jack Dempsey; other situations/conditions can cause them to become aggressive. They tend to be more aggressive when kept in a tank that is not spacious enough to help them live their life to the fullest – one may not be wrong to conclude that they do not take getting stressed lightly.

Also, these very freshwater species get more aggressive as it ages; the juvenile forms appear to be more even-tempered than the adult. And it is worth stating that it is easy to know whenever the Jack Dempsey fish is full of fury; they pick up a darker body coloration at such moments – so, in a way, Jack Dempsey is no pretentious creature.


Though they may be predatory- which makes some people classify them as ‘carnivores’ – the Jack Dempsey fish are omnivores when it comes to feeling. 

What food is right for Jack Dempsey Fish? Jack Dempsey fish food can include pellets, flakes, shellfish, tubifex, brine shrimp, bloodworm, thawed seafood, etc.

They also like vegetables such as cabbage, lettuce, and blowball leaves; all these must be well chopped and do take care to make every other food available in sizable bits for the ease of consumption.

They can consume different kinds of food, although they seem to have a great appetite for meaty diets. 

In a bid to feed your pet with a diet rich in protein, it is advisable that you avoid foods like beef heart and Poultry meat as these could bring about some digestive complications, especially when the fish is overfed with them. Plus you should be mindful only to provide a substantial amount of feed that can be consumed in under 3 minutes.

On the feeding frequency; you should feed your Jack Dempsey fish once or twice every day.


The Jack Dempsey fish are not so demanding as they can thrive in a wide range of water conditions, and also feed on different kinds of food; this is some of the reasons many aquarists[and even beginners] in particular have come to adopt them as their aquatic pet of choice.

    Despite their hardiness, however, it is essential that you do not leave them to dwell in a water environment that is loaded with nitrogenous compounds such as ammonia, nitrite, and nitrate. A build-up of these compounds in the tank may result in the breakout of diseases.

    How long does Jack Dempsey live? A jack Dempsey fish can live up to 10-14 years in an aquarium. 

    Tank setup

    The Jack Dempsey fish are found in slow-moving– or even still – warm water with a sandy bottom and a lot of hiding spots, and it is with this in mind that I shall now proceed to discuss the tank setup.

    What tank size is right for Jack Dempsey? Jackey Dempsey should be housed in a tank with a minimum carrying capacity of about 190 liters – and maybe a bigger tank depending on the number of fish you are attempting to keep therein. The tank should have a dark sandy substrate – finely grained sand should be utilized.

    To provide your Jack Dempsey fish with the needed hiding spots, you can use caves, stones, and rocks – these should be placed into the tank even before filling the bottom with the sand to prevent them from falling off as the fish burrows.

    You can also decorate the tank with items such as bogwood and plants [like Java fern, Sagittaria andanubias] that cannot be easily destroyed when Jack Dempsey goes on a furious trail.

    The tank should also be equipped with a highly efficient filtration system that should be positioned on the outside.

    For the lighting; Jack Dempseys prefer low or moderate lighting; they tend to be more active and less stressed under such setting. Owing to this, you should endeavor to place the tank at a spot where sunlight penetration is minimal.

    Permit me to chip this in: we all have different for keeping aquarium fishes, but beyond satisfying our hobby, having a Jack Dempsey in a well-set tank surely does the home interior a whole lot of good.

    Water parameters

    Jack Dempsey fish can tolerate poor water quality to some extent, but this would undoubtedly shorten their lifespan. So, it is of importance that you have them in a conducive (water) environment that would promote good health. In this wise, you should ensure that the following water chemistry is sustained within the aquarium at all times:

    • Water temperature: Jack Dempsey fish thrive in warm Waters making a temperature of between 26°C and 27°C perfect for them, but they can also survive in temperatures as high as 30°C. It has also been reported that they can survive in a lower temperature of about 16°C – yet another testament of their tough nature.
    • Water hardness: They will be fine in moderately soft to the very hard water with the range being between 5dH and 19dH.
    • PH range: The pH range for the Jack Dempsey fish is between 6.5 – 7.5, slightly acidic or slightly alkaline.
    • Water change: A water change of 20% should be carried out every two weeks.


    Bearing in mind that the Jack Dempsey fish is a predatory species when attempting to select tank mates for them, you will have to look away from relatively smaller fishes that can be easily feasted on by Jack Dempsey.

    Jack Dempsey fish tank mates can be Oscars, firemouth cichlids, kissing gourami, koi, angelfish, cave tetras, and green terror. And, you could yet keep a group of 3 – 4 Jack Dempseys in the same tank.

    The size of the community tank must be appropriate for the number of Species being kept so as not to make your pet inconvenient thus sparking off its aggressiveness. You should not hesitate to intervene – by putting them apart – whenever you see your Jack Dempsey in a fight with other tank mates.

    Sex differences

    Differentiating between the male and female Jack Dempsey fish is not so much of a difficult task. All you have to do is to pay close attention to a couple of features. So, to start with; the dorsal fin and the anal fin of the male Jack Dempsey fish are usually longer and pointier than those of the female.

    Generally, the male is larger than the female and is usually more brightly colored. Furthermore, the spots on the body of the female are known to be fewer than what is found on the male’s body. Behaviorally, male Jack Dempsey fish tend to be more aggressive than the female.

    Pre-breeding conditioning

    As you anticipate having a successful breeding session [with a Jack Dempsey pair], it is expedient that you set the conditions aright. Putting first things first; you should separate the male from the female by using a divider to compartmentalize the tank, or you can put each one [of the pair] in a different tank altogether if you can afford it. The couple should be fed with protein-rich diets for about 3 – 4 weeks with the temperature set at 28°C.

    Note that this separation should only go ahead after you must have found a compatible Pair – that is, male and female that get along very well. Again it is worth noting that the success of the spawning session is usually dependent on the age of the fish; Jack Dempsey should reach sexual maturity at the age of one –they may however reach sexual maturity at a younger age in some instances.

    The breeding tank should be set up prior to bringing the pair together. It is essential that you create a very clean substrate and maintain good hygiene within the tank. Plus items such as caves, flower pots, etc. should be made available as they will need these along the line – while the spawning session lasts.


    Jack Dempsey fish are typically more hostile during spawning, and upon being ready to spawn, the pair pick out a choice substrate on which mating will take place. The female eventually moves to lay the egg around a corner or in a hiding spot; the male follows after her to fertilize the eggs. The Jack Dempsey fish are quite productive as they are capable of laying up to 500–800 in a single breeding season.

    It is not strange to see the female digging up pits where she would eventually hide the eggs.

    One commendable characteristic of Jack Dempseys is their parental instinct which is quite impressive – both parents have a role to play in ensuring the safety of the Offspring; the female gets to watch over the brood while the male takes charge of territorial defense. And, it is even more interesting to note that the female could become infuriated [and fight] with the male if he fails to do his job dedicatedly.

    However, you may need to come in upon noticing any fight in the breeding tank. In such a scenario, all you need to do is withdraw the male from the breeding tank. Failure to do so could result in them fighting to the death, or a situation whereby they end up consuming the eggs.

    Post-breeding care

    The fertilized egg should be hatched in about 3 – 6 days, but the fry will not be able to eat until they are nearly 8 – 10 days old.

    Even when they start eating, they will not be able to take the same portion of feed as the adult. At this point, it’s best to feed them with pulverized fish feed or infusoria. The parents yet show their caring attitude in this regard by masticating considerably big chunk (of food) into the size their juveniles will find easy to munch on.

    For the development of the juveniles; you should ensure that the optimal tank conditions are sustained, and do regular small water changes – say, 25% water change every week.

    Again, considering the number of juveniles in the tank you may have to find a way of managing the population of the fish in the tank – culling is the method that is often adopted to control the population.


    Despite their hardiness, Jack Dempseys may also get downed by some diseases which affected by freshwater species, and as observable in most diseased conditions affecting aquarium fishes; poor water quality and unhealthy diet are usually the primary causes. The introduction of an infected species may also lead to the breakout of diseases in the tank.

    So without further ado, let us look at some of the diseases that can affect the well-being of your Jack Dempsey:

    • Head and Lateral Line Erosion (HLLE): Also known as a hole in the head, this disorder is reported to be caused by lack of certain vitamins as well as poor water condition. It could also be caused by a particular bacterium known as Hexamita, which is why the disease is sometimes called ‘hexamitasis’. The condition can, however, be exacerbated by stress or a weak immune system.

    The most common sign of this disease is the emergence of lesions in the head of the affected fish; holes can eventually show up around the fish’s head and body if the condition is not treated early. Infected Jack Dempsey fish will also experience discoloration and loss of appetite.

    Hole in the head has been treated using what I will like to refer to as ‘combination therapy’ whereby vitamin supplements and improved nutrition, as well as a number of antibiotics, have been useful for curing the disease. Treatment is usually tailored towards addressing the root cause; for instance, antibiotics will be very much required in the situation whereby the disease is caused by Hexamita.

    • Skin fluke: Skin flukes, Dactylogyrusspp. and Gyrodactylus spp. are capable of attaching themselves, with the aid of a specialized organ, to the body of the fish – the skin and gill in particular. The activity of these flukes is what leads to the manifestation of disease. As they begin to spread, lesions start to appear on the fish’s body and bring about the excessive production of mucus.

    Additionally, the fish may suffer weight loss; become restless, and may sometimes rub its body against rocks and other hard surfaces. Fungal and bacterial infections may also occur as the immune system of the affected fish becomes dysfunctional or impaired.

    Several medications like anthelmintics, formalin, praziquantel, and some organophosphates have been found to be highly potent in getting rid of skin flukes.

    • Freshwater Ich: This is arguably the most common disease affecting freshwater species, and cichlids [of which Jack Dempsey fish is one] are known to be prone to it. A Jack Dempsey fish infected by the parasite causing this disease will develop white spots on its body; experience respiratory complications; appetite loss; swim in an uncoordinated fashion, and even go into hiding more than it would typically do.

    Heat treatment and medications such as formalin and malachite green have been used, to significant effect, in taking care of fishes having freshwater ich.

    Apart from the disorders discussed here, there are other parasitic diseases that the Jack Dempsey fish may be susceptible to, and it is incumbent on you to be committed to your fish’s well-being. The trick to having it around for a long while is simply in doing what is needful as at when due.


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