Jack Dempsey fish

Jack Dempsey (Rocio octofasciata, earlier called Cichlasoma octofasciatum) is a widely spread tank fish within North and Central America.

Because of the fish congenital aggressiveness towards its tank mates the USA aquarists have called it Jack Dempsey by the name of the popular professional boxer.


Inhabitance in the wild

The species has got Rocio name by the name of its describer’s wife; in Spanish “rocio” means “dew” and indicates the presence of sparklet-spots in the fish coloring.

Specific name of the fish “octofasciata” comes from Latin words “octo” (eight) and “fascia” (a belt or a stripe) and it is translated as “eight-striped”.

In fact the fish has definitely more than eight stripes on its body.

Jack Dempsey fish is native to Central America Atlantic hillside waters. It inhabits all around from the Ulua river (Honduras) to the Papaloapan river (South of Mexico).

The fish may be also encountered in Guatemala, Belize region. Jack Dempsey fish was artificially settled into the waters in the USA South (in the state of Florida and some other areas close to the Gulf of Mexico) and Thailand waters.

Shallow rivers with clean water and small spring-fed lakes are the biotopes more common for this fish.

However, this species may be also encountered in low flow and even slough waters, which quite often have soft muddy bottom.

The fish that has become naturalized in the USA quite often inhabits in plant-filled channels and water furrows with muddy or sandy bottom.


Rocio octofasciata is a middle-sized Cichlasoma species. Rocio octofasciata male size is up to 21 cm long (8.27 inch), the female fish is up to 17 cm long (6.69 inch).

However, in the wild the male fish isn’t more than 12-15 cm long (4,72-5,91 inch).

Jack Dempsey fish body coloring is olive-drab and when the fish is angry or during its spawning period it gets much darker and becomes almost black. Each scale of the fish body, its opercles and fins have some sparkling spots on them, which depending on light and the fish state can seem blue, cyan or golden.

Jack Dempsey female fish is colored less brightly. Rocio octofasciata juveniles have stripes on their bodies, but they aren’t very clear and there are more than eight of them, usually it’s ten or even eleven. The adult fish has some signs of these stripes on its forehead, back and abdomen, but rich colored adult Rocio octofasciata males have these stripes only on their forehead.

There are some eyespots on the fish body sides and tail, which are rather clearly seen on Jack Dempsey fish juvenile’s body and barely seen on the adult fish body.

Jack Dempsey fish iris is gray with some bronzy tint. The fish dorsal is red-edged.

There is also a blue colored species of this fish – it’s widely known «Blue jack dempsey» or «Electric blue jack dempsey». In comparison with classical Rocio octofasciata, Blue Dempsey has bright cyan coloring, it has smaller body and it is less aggressive.

From hearsay this unusual kind of Rocio octofasciata is considered to appear as a result of breeding with some other cichlid species, just like Flower Horn appeared. However, another point of view is considered as more convincing, that this bright blue variation of Jack Dempsey fish is one of the latest and the most impressive genetic mutations that are observed among tank fishes.

Such variation of Rocio octofasciata is much more seldom seen, since to obtain it you have to be good at genetics and some bright colored and high-quality breeders are required for this.

Electric blue jack dempsey
Electric blue jack dempsey

Difficulties in keeping

It’s quite simple to take care of Rocio octofasciata, since it’s not demanding, so it can be kept by the beginners. However, you have to keep in mind that this is an aggressive fish that get’s on well with other cichlid species while it’s young, but as the fish grows it becomes more and more aggressive, so then it’s desirable to keep it without any other tank mates or only with large fishes.


This Cichlazoma is a predator, so you should feed is with live feed: brine shrimp, blood worm, tubifex, though thawed and milled seafood will do as well. However, you shouldn’t forget about plant additives – these may be finely chopped lettuce, cabbage or blowball leaves.

You should treat all of these with boiling water first before giving them to the fish. Feed the fish once a day to avoid overfeeding.

Keeping in a tank

As a majority of Central America cichlids Rocio octofasciata doesn’t have any special requirements as for the tank conditions. Nevertheless, the tank water should be clean, i.e. with zero level of ammonia and nitrite, and nitrate concentration shouldn’t exceed 40 mg/l.

Nowadays, all these can be reached by means of strong biofiltration and regular water renew. Rocio octofasciata tank size capacity should start from 100 liters (26,42 gallons) for a couple of adult fish.

In fact, this species aggressiveness to a large extent depends on the fish tank size. In small tanks (up to 250 liters or 66,04 gallons) an adult couple of Rocio octofasciata, as a rule, can’t stand any tank mates around, unless it be some catfish or very small fish and juveniles.

In small tanks also there may be fights between the fish male and female. If this happens, you should immediately take the female fish away from the tank.

Keeping the fish couple for 3-6 month together and then for 1.5-3 month or more apart, is considered to be ok if you keep Jack Dempsey fish couple in a small tank (in a big tank the female fish just swims to its other side and usually the male fish doesn’t chase her).

Also the fish isolation from each other is a way to decrease the number of their spawning, since doing it too often isn’t healthy for the fish, especially for Jack Dempsey female fish.

Quite often this species inhabits in rather poor conditions due to their careless owners and seem to show rather high vitality. However, this plainness is rather nominal.

Young Jack Dempsey fish can actually inhabit in tank water polluted with nitrogen compounds, however, very few of the fish live to the age of 4 years old. Negative influence of toxic substances accumulates and then when the fish becomes an adult it shows in the form of hexamitiasis and other diseases.

Meanwhile, provided with proper care Rocio octofasciata life span in a tank is about 7-10 years and more.

When the water temperature becomes lower than 24°С (75,2 F) the fish tends to stay close to the heater. Therefore, we can consider water temperature 26–27°С (78,8-80,6 F) as optimal one for Rocio octofasciata.

When preparing Rocio octofasciata tank you should foresee the presence of some nookeries in it.

Also keep in mind that this fish doesn’t like bright light and it’s more active during half-light period.

However, the main warning when keeping Rocio octofasciata in a decorated tank is the fish “vandalism” towards any tank plants.

In general, it’s possible to put some plants in a tank with Rocio octofasciata, the fish doesn’t eat them, but it can harm them once it decides that the plants don’t belong here.

Scientific NameRocio octofasciata, Cichlasoma octofasciatum
Common NameJack Dempsey, Electric Blue Jack Dempsey
Tank size100 liters (26,42 gallons) and more
Temperature75–81 °F (24–27 °C)
Size17 cm (6.69 inch)

Sex differences

Rocio octofasciata male is larger, more deep bodied and brightly colored. The adult fish body is almost all covered with sparklets. Male fish genital papilla is antrorse (it has a shape of firing hammer), the female fish genital papilla looks like upside-down blunted cone.

Another difference, but it’s not a 100% hall-mark, is the presence of cyan spots on bottom side of the female fish opercles, which the male fish doesn’t have.

When buying Rocio octofasciata juveniles keep in mind that at the age of about 3-4 month the female fish is quite often larger than the male one. So, in this case you shouldn’t use the fish size to define its gender.

However, if you take some time to observe the fishes you’ll be able to define it even when the fish is that young. Rocio octofasciata males from their early days start showing their territory dependence and protect their nookery by trying not to let other juveniles in it.

When they become aggressive their coloring gets darker, then the female juveniles have. When observing Rocio octofasciata fish “teens” you can define their gender by the pointed dorsal the male fish has and the rounded one the female fish has. However, later both the fish male and female have a pointed dorsal.


In spacious tanks Rocio octofasciata doesn’t show such an aggression, like they may do in small capacity tanks, therefore you can keep the fish together with other equal-sized cichlid species (Convict cichlid, Firemouth Cichlid, Blue acara, Green terror).

You shouldn’t keep Jack Dempsey fish with any small fishes, since they’ll be eventually eaten, though Jack Dempsey fish isn’t a complete predator.

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In the wild the fish becomes reproductive at about the age of 12 month. As for Jack Dempsey fish kept in a tank, they become reproductive at the age of 6 month already. When the fish “teens” are kept together in one tank they create couples themselves.

Forced formation of the fish couple may be rather troublesome, since Jack Dempsey fish males are rather demanding in this respect. So, if you aim to create the fish couple not for just one spawning, it’s better to let the fish male choose his mate on his own from several female fish “teens”.

This approach is obviously the optimal one in the context of minimization of conflicts inside the fish couple, since predeterminedly smaller and younger female fish has more mild nature and behaves correspondingly.

If the dominating female fish shows aggression and tries to hustle away other female fish, it’s better to take her away from the tank, because there are high chances that the male fish will have to choose her.

Jack Dempsey fish perform pare spawning on a substrate. The fish may use different subjects as a substrate: large flat stone, flower pot or some section of a tank bottom cleaned from the substrate. There were also cases when Jack Dempsey fish just like dwarf cichlids laid their eggs inside their nookery. The fish terribly digs the tank bottom, creates parapets along the tank walls and damages tank plants.

It’s better to get separate tank for Jack Dempsey fish spawning. If you have a wels catfish (sheatfish) in the tank together with Jack Dempsey fish couple, it’s advisable to take the catfish away from the tank for a while, since it may eat the spawn or become the reason of Jack Dempsey fish fights.

It’s quite peculiar for Rocio octofasciata to take care of their juveniles, so you won’t need to perform any special actions like taking away ill eggs from the spawn or installing aeration near the nest. The fish do everything on their own. On the contrary, it’s better not to disturb the fish if it’s not necessary.

The eggs grow for 3-6 days (depending on the temperature and other parameters). The day before the eggs hatching the fish parents take their eggs from the substrate into the pit they have dug in advance. Don’t let this confuse you and decide that the fish has eaten their eggs.

There also may be several such pits. In this case the fish hides their eggs several times a day from one pit to another. And if there’s no substrate in a tank, but there are some plants in pots – these will also do for the fish.

The fish larvae start feeding on their own about 4 days later. Start feed for them may be the following: brine shrimp nauplii or some artificial feed. The fish parents split their responsibilities as for their spawn: the female fish takes care of the eggs, juveniles and larvae, the male fish guards their territory.

In the real life this is the reason for conflicts. The female fish may get angry with the male one because he is taking care of the hatch too eagerly or he is guarding the territory not thoroughly enough. In the worst-case scenario this leads to the fight inside the fish couple and eating their eggs or larvae.

That’s why it’s better to isolate the male fish right after the spawning is over or a bit later – when the juveniles start to swim, since he will just make the female fish nervous with his clumsy actions. Therefore, if there’s no other fish in the spawning tank – there’s no need to protect it.