Jack Dempsey: Diet | Size | Breeding | Lifespan | Sexing | Care Guide

I’m going to hazard a guess here and say that when you hear the words Jack Dempsey (rocio octofasciata) you don’t really know what to think? Are they a highly aggressive species? Are they just semi-aggressive? Or are they actually the ‘pussycat’ of the cichlid world? Ask ten different keepers and you’ll get twelve different answers!

Within this ultimate guide to the Jack Dempsey cichlid, we will attempt to answer these questions and many, many more that you might have. We will cover every angle of Jack Dempsey care and get you better acquainted with this magnificent fish.

Jack Dempsey Characteristics and Care

With the common name Jack Dempsey, it is not surprising that people will automatically think of this fish as being an aggressive bruiser. After all, you don’t name something after a boxing legend for nothing! However, if you stop for a minute and forget the common name leaving only the scientific one behind, it paints an entirely different picture.

Rocio Octofasciata, the scientific name allotted to this species, translates literally into ‘dew eight stripes’ which is a far cry from the more aggressive common one. Rocio is the Spanish translation of dew, whilst octo refers to eight, and fasciata belt or stripe. This paints a completely different picture of the Jack Dempsey, doesn’t it?

This gentler image we now have is in reference to the spots that sparkle in the light, and the stripes which run vertically down its body. These stripes, however, are not blatantly obvious on every fish, unlike the spots which really make the Jack Dempsey a showstopper.

Care wise the Jack Dempsey, perhaps surprisingly, is amazingly easy to keep providing you meet their basic requirements and are careful about the environment you choose for them. They do, however, need rather large aquariums which will mean they are not suitable for every home purely due to space.

Below is a rough guide to basic requirements of the Jack Dempsey (rocio octofasciata) for you to peruse including minimum tank size and the type of environment they need.

Scientific NameRocio octofasciatum
OriginFarm Raised,Central America
Diet Carnivore
Care LevelEasy
ColorBlack, Blue, Clear, Green, Tan
Tank Size50 Gallons Plus

Color and Appearance of the Jack Dempsey

The Jack Dempsey is undoubtedly a large thick-set species but not one that typically represents a predator. They are, in fact, far too pretty to be given that label regarding looks!

The coloration of a Jack Dempsey will change as the fish matures. Usually, as a juvenile, they are light gray to tan developing into dark purple-gray as they age. Markings will start as a faint turquoise fleck and develop into a very bright and iridescent bluish-green and gold flecks. The Jack Dempsey appears to sparkle like the morning dew.

Jack Dempsey
Jack Dempsey (Photo Credits @Outlierforlife)

The female of this species tends to be less colorful than the male and is in general smaller. Males reach approximately eight inches in length in the home aquarium whilst the female only reaches around six.

The male also has a dorsal fin and anal fin with a long pointed tip whilst the female is more rounded. Interestingly, both sexes of Jack Dempsey will immensely darken in color to almost black when they are under stress.

It should be noted here that there is a second coloration type of Jack Dempsey which is the electric blue. Not surprisingly, it is much bluer in coloration. A debate, however, surrounds this mutation as it seems that it cannot be agreed upon how they developed.

Some people claim it is just a plain and simple genetic mutation, whilst others believe it is the result of breeding the Jack Dempsey with other cichlid species.

Where Do Jack Dempsey Cichlids Come From?

The Jack Dempsey is found naturally throughout the Central American region in countries such as Mexico, Honduras, Guatemala, and Belize. They have, however, also been found in the waters of Australia, Thailand, and other parts of America too. This is not a natural territory nonetheless, rather they have been introduced into the water systems by people placing them there.

Preferring hard alkaline waters the Jack Dempsey is most commonly found in the warm but sluggish waters in swampy areas, drainage ditches, canals, shallow rivers, and spring-fed lakes. Should you be lucky enough to go seek them out be sure to comb through the weeds where they are most likely to be lurking. They are not mentioned on the IUCN Red List and so are thought of as a common species.

In their natural environment, Jack Dempseys feed upon worms, crustaceans, small fish, and various insects.

jack dempsey fish - fishkeeping forever
Jack Dempsey fish – fishkeeping forever (Stunning Jack Dempsey Fish Showing All Its Colours)

Are Jack Dempsey Cichlids Aggressive?

The Jack Dempsey was, as we have already discussed, named after William ‘Jack Dempsey’ Harrison who was a 1920s American heavyweight boxing champion. This was due to the species growing reputation as a bruiser of the aquarium, and its high levels of aggression. No fish, it was said, was safe in with this predator, which would have a pop at anything and everything!

The truth, however, about this species is that the majority do not live up to the reputation that lingers with them. Yes, there are Jack Dempseys out there that are crazy aggressive and will attack anything and everyone but most actually will not. In fact, it is estimated that only around 30% of Jack Dempseys in the home aquarium deserve the reputation they have got.

A good description of the Jack Dempsey would be that it is calm but in an eccentric way, and has fairly good manners. This does not mean that they are suitable for a community aquarium as they are far from that.

They will, however, do well, in the main, in a mixed predator tank. Of course, there are exceptions to this rule and you need to be careful and monitor the behavior of your Jack Dempsey and other species together.

Jack Dempsey can also be incredibly shy, especially when first introduced to an aquarium. This will show in their unwillingness to swim in open water, preferring to hide out in amongst plants or in caves. They will generally settle over time although they may never be gregarious.

Being territorial is another natural trait of the Jack Dempsey which will establish territory and defend it vehemently. This is especially true should they be breeding or when there is a small amount of fish in the aquarium. The Jack Dempsey fairs better and behaves better in a busy aquarium.

It is also worth noting that Jack Dempsey’s are very adept at aquascaping and will rearrange your aquarium to their liking. This means uprooting plants, digging holes in the substrate, and moving or knocking over ornamental pieces.

Jack Dempsey Species Profile

With a lifespan of seven to ten years, the Jack Dempsey is a long-term commitment. They are, however, relatively easy to keep providing, as stated previously, you provide the right environment for them. This means a suitable sized aquarium, suitable tank mates, suitable diet, and frequent aquarium maintenance.

The minimum aquarium size recommended for a Jack Dempsey kept alone is around 50 gallons. To keep them in groups or with other species, however, it will need to be much larger. Five to six-foot aquariums are the usual recommendation here.

As Jack Dempsey are messy eaters and produce a high quantity of waste, you will need a quality external filter that produces a good rate of water movement. Water parameters should be kept at around 22-30℃ or 72-86℉, and a pH of 7-8. Read our review of the best filters for larger aquariums.

Decor-wise a sand or small gravel substrate of approximately 2 inches or 5 cm deep should be provided as Jack Dempsey like to dig and sift. This is especially true when breeding as the male will dig a hole to hide the newly born fry in.

Jack Dempsey’s prefer a natural style aquarium with bogwood, large rocks, and caves. Be sure to create areas where they can set up territory with your decor items as Jack Dempsey’s are very territorial. It is also a good idea to put tall and vertical items in the aquarium to break lines of sight and ease tension between them and other fish.

Decor and Lighting

Be careful if you choose to use live plants for breaking lines of sight as the Jack Dempsey is adept at uprooting them. You can, however, get around this by using either fake plants or keeping live plants in pots rather than rooted into the substrate. Java fern and anubias are also good aquatic plants to try as you can secure them to rocks and wood.

As Jack Dempsey are more active in subdued aquarium lighting, it is a good idea to provide them with that very thing. They do not tend to like a bright light and may become shy and reclusive if subjected to it. A tight-fitting lid is also a good idea with this species as if they do decide to jump a flimsy cover is not going to stop this large growing fish from escaping.

Once you have the correct set up for your Jack Dempsey, you will need to decide how many you wish to keep. Singular specimens will do well in a mixed aquarium and larger groups of four to five too. It is not recommended to keep Jack Dempsey in pairs as this can lead to aggression.

aquarium bogwood
(Aquarium Bogwood On Amazon)

Jack Dempsey are usually purchased as juveniles of around 2-3 inch in size. At this period in their lives, it is virtually impossible to sex them although young males may be obvious as even at this young age they will be dominating the breeder’s aquarium.

If you want to be more definitive about the sex of the Jack Dempsey you choose you, will need to wait until they grow to around four inches when the differences between the male and females become more obvious. We will cover sex differences later.

You can purchase Jack Dempsey relatively easily with most pet and aquatic stores and online sites keeping them. Beware, however, if you do decide to buy a pair as many keepers have fallen foul of buying accidental same sex pairings.

This usually occurs because the pair are siblings so will tolerate each other leading to the belief they are male and female. The best way to avoid this is to buy pairs if you must, that look very different to each other.

Once you have your Jack Dempsey, you will need to acclimate them to your aquarium. As they are hardy fish that can tolerate water parameter fluctuations well, there is generally no need for elaborate acclimatization such as the drip method.

Once in your aquarium, you will need to keep an eye on your Jack Dempsey to ensure they are settling in and that there are no signs of overt aggression. This will be especially true if it is a mixed species aquarium as there are no guarantees with Jack Dempsey that they will tolerate other species.

As stated previously Jack Dempsey are a hardy species that will flourish in a healthy aquarium. They are, however, susceptible to illnesses such as ich, hole in the head, skin flukes, and infection should the water condition become poor. Regular maintenance of your aquarium, however, will prevent these.

If your fish becomes ill or starts to show unusual behaviors then read our complete guide to diagnosing and treating many of the common diseases in our complete guide.

What do Jack Dempsey’s eat?

The Jack Dempsey is a carnivorous predator that feeds on worms, insects, small fish, and crustaceans in its natural habitat. All these things are readily available in the aquarium trade should you wish to keep their diet natural.

We also find API Cichlid Pellets are loved by many of our cichlids. It’s inexpensive and top quality.

Other foods your Jack Dempsey will eat include brine shrimp, bloodworm, talapia, chopped lettuce, cabbage, and live feeders. You can also use a cichlid pellet but this will need to be of high quality. As a treat beef and poultry can be given but this should only be in small amounts. Best Cichlid Food Here!

As with many other species a varied diet can be key in keeping your Jack Dempsey healthy and growing well. A suggested feeding schedule would be three days of a high-quality cichlid pellet, one day of live feeders, and the remaining three days a mix of crickets, leaches, worms, etcetera.

Never over-feed any fish especially messy eaters like Jack Dempseys. Read our article which tells you what to do if you have overfed your fish.

How Do You Sex and Breed Jack Dempsey Cichlids?

Male Jack Dempsey are larger than the female with a bigger head and long pointed tips to their anal and dorsal fins. They also tend to be more colorful than their female counterparts. Females tend to have a less pinkish base color and have blue speckling on their lower jaw.

Breeding Jack Dempsey is extremely easy, in fact so easy you should proceed with caution. This species will easily spawn far more fry than you can re home! They will do this in both breeding aquariums and community ones.

The mating ritual will begin with the male shaking to show himself off to his potential mate. Once paired up they will both turn black and look extremely imposing. Jack Dempsey are monogamous and will pair for life.

Spawning will take place underneath overhangs, in caves, in pipes, in fact anywhere that they can get under. Both male and female will become more aggressive when breeding although it is the female who becomes crazily so. She will look after the eggs and fry whilst the male will guard the territory.

After three to six days the fry will be born and the parents will herd them into a pit that the male Jack Dempsey will have prepared. He will do this by digging out the substrate to create a hole. Again the female will look after the fry whilst the male guards the territory. Fry will start to eat at around four days old.

Another word of caution needs to be added here regarding adding a female to a male. The male instantly upon seeing the female will want to mate and start to be amorous. Should the female not be receptive instantly to his advances he will tell her to leave which of course in an aquarium she cannot do.

When the female does not leave, the male Jack Dempsey will proceed to bully and attack her. This will result in the next day the keeper of these fish more than likely finding the female close to death. To avoid this, it is imperative that the male and female are kept separate with a divider until the female ripens and is ready to mate.

Suitable Tank Mates

Regarding Jack Dempsey and tank mates, there are only two certainties. One is that no smaller fish should be kept with this species as they will be eaten, and the second that they are not suitable for community aquariums.

Jack Dempsey should only be kept in species only or predator aquariums. This still, however, is no guarantee that they are going to get along. Pairing Jack Dempsey with suitable tank mates is incredibly hit and miss and will need careful monitoring.

Possible tankmates include severums, oscars, blood parrots, Plecostomus, and various other cichlids. These are convicts, firemouths, blue acara, and green terror. Basically, to have any chance of success tank mates need to be able to hold their own!

Conclusion: Jack Dempsey Care Guide

There can be no doubt that the Jack Dempsey Cichlid has gained itself a reputation as one of the bad boys of the aquarium, and perhaps this was once deserved. However, as time goes on as with all other species, it has mellowed and developed into a lesser aggressive fish.

What we have now is a quirky character, a weirdly attractive fish that is full of good manners, eccentricity, and a little aggression thrown in. They are true characters of the aquarium and deserve relabeling as such.

If you’re just starting out and looking for some helpful information on how to start a fish tank for beginners, then feel free to read our complete guide. You may find it very helpful and it should stop you from making some of the common fish keeping mistakes.