Jack Dempsey: The 2024 Care Guide!


Jack Dempsey: The 2024 Care Guide!

The Jack Dempsey is an old favorite in the aquarium trade and aquarists for generations have enjoyed keeping these sizable, personable fish! They are one of the best cichlids for beginners interested in trying to keep medium to large fish because they are not only hardy but beautiful as well!

Jack Dempsey Care Guide

Characteristic Detail
Scientific Name Rocio octofasciatus
Adult Size 8-10 inches
Temperament Semi-aggressive; Territorial
Lifespan 8-10 Years
Care Level Beginner
Water Temperature 73-78℉
Appearance Gold and blue spangled with a dark purple to black background
Water pH 7.0-8.0
Diet Carnivorous
Tank Size 55+ Gallons


Jack Dempsey Overview

Typical Jack Dempsey Behavior

Jack Dempseys get their name from the legendary boxer and 1919-1926 world heavyweight champion Jack Dempsey! At the time these were some of the most aggressive fish to be found in the hobby and over the years both the name and the reputation has stuck.

But truthfully, Jack Dempseys are semi-aggressive at best. Sometimes you can find a truly temperamental fish, especially a large male used to living alone. But there are quite a few cichlids that are much meaner. So long as you provide plenty of space for tank mates Jack Dempseys can be kept with other fish.

Jack Dempsey Appearance

Jack Dempseys are quite beautiful as they mature. When young they have a faint pattern of gold and blue spangles against a brown background. But as they grow up the brown deepens to purple or even black in tone and the spangled scales increase in size and number.

There are also Electric Blue Jack Dempseys, which are completely covered in brilliant blue and black scales and usually have red eyes. They also have longer fins and usually end up slightly smaller as adults. Electric Blue Dempseys are a little more sensitive than regular Jack Dempseys because they are deeply inbred to achieve their colors but otherwise identical in care.

Life Span

Like most large cichlids the Jack Dempsey is a fairly long-lived fish. 8 to 10 years is pretty common for a well-cared for Dempsey and 1 to 2 more years on top of this is not unheard of.

How Big Do Jack Dempseys Grow?

The Jack Dempsey is an upper medium-sized cichlid, with males growing 8 to 10 inches long on average. Females may be an inch or two smaller but no more than that. Both sexes are quite stocky as well.

Sexing Jack Dempseys

Telling apart male Jack Dempseys from females is a little more challenging than with other cichlids but not impossible. The sexual characteristics are more subtle but with a little practice you can pick them out with ease!

A male Jack Dempsey will always be slightly larger than a female of the same age. He will have slightly more pointed dorsal and anal fins and he may even have a hunched back.

Females are smaller and may display pointed dorsal and anal fins but not nearly so strongly as a male’s. They also have brighter blue spangles along the jaw and under the eyes. A healthy adult female will often be more robust than a male as well since her ovaries take up additional space in her body cavity!

Compatible Tank Mates for Jack Dempseys

Choosing tank mates for a Jack Dempsey isn’t as hard as it’s often thought to be. These cichlids are semi-aggressive at most. So stick with peaceful, fast moving tank mates or other semi-aggressive fish (assuming the tank is at least 55 gallons in size).

Quick, peaceful fish that are too large to be eaten include Silver Dollars, adult Tiger Barbs, Denison Barbs, and Giant Danios. Unfortunately, smaller fish like Guppies, Bettas, and Platieswill simply be eaten by an adult Jack Dempsey.

Large, slow moving, peaceful fish like Angelfish are also a bad idea since they will be harassed relentlessly. Instead, stick to larger semi-aggressive fish like Blue Gouramis and Arowanas. Cichlid tank mates can also work, though they need to be chosen with extra care because they may fight if their size, temperament, or tank size aren’t well matched. Semi-aggressive cichlids that are a match for Jack Dempseys include Oscars, Convict Cichlids, and Green Terrors!

Good Tank Mates for Jack Dempseys Include:

  • Silver Dollars, large Barbs, and other Dither Fish
  • Larger Gouramis, medium sized to large Cichlids, Arowanas, and other Community Fish
  • Plecostomus, predatory Catfish, Stingrays, and other Bottom Dwellers


Water Conditions for Jack Dempseys


Jack Dempseys are tolerant of a wide range of tropical conditions. Anywhere from 70-80℉ is fine for them, with the middle range of 73-78℉ being best!

Water Chemistry

Jack Dempseys come from Central America – Southern Mexico, Guatemala, and the like. Here the water tends to be not only warm but slightly alkaline thanks to all of the limestone in the region. Therefore your Jack Dempsey will feel right at home in the alkaline tap water that’s common in the United States and other parts of the developed world. The dissolved minerals will keep the pH right around 7.1-7.6, which is perfect for them.

That said, if you have neutral to slightly acidic conditions a Jack Dempsey won’t be too bothered. Acidic extremes (pH<6.8) should be avoided, though.

Jack Dempseys are also very hardy and resistant to temporary increases in ammonia, nitrite, and nitrate. Still, we don’t want to keep them in poor water conditions for very long. As carnivores they create loads of waste so having a powerful filter is essential for their health. Also remember that Electric Blue Jack Dempseys are more sensitive to high concentrations of nitrogenous waste compounds and can be killed by water conditions that would not affect a standard Dempsey.

Tank Setup for Jack Dempseys

Tank Size

The only real hassle when keeping a Jack Dempsey is planning for their eventual adult size. They are usually sold as cute little 1 to 2 inch juveniles. Since an adult male can reach 8 to 10 inches in length they need a spacious aquarium over the long term.

55 gallons of space is an absolute minimum since these tanks are 12 inches wide, giving the Jack Dempsey just enough space to comfortably turn around. A 75 gallon is even better, especially if you plan on keeping your Dempsey alongside other semi-aggressive cichlids so they can carve out their own territories.

Feeding Your Jack Dempsey

What Should I Feed My Jack Dempsey?

Jack Dempseys are carnivorous cichlids, feeding on smaller fish, worms, shrimp, snails, insects, and other aquatic life. Therefore we want to stick to protein-rich food sources. Prepared pellet formulas make a great basis for their diet so long as you take a moment to read the ingredients label.

Many formulas use cheap fillers like wheat and potato starch, which are poor quality sources of nutrition. Look out for fish meal, shrimp, and other higher quality ingredients when shopping for cichlid food!

Besides prepared pellet formulas you should also offer a Jack Dempsey fresh and frozen items to fill in any missing vitamins and minerals. Earthworms, strips of white fish, chopped shellfish, and the like are perfect for these carnivores.

While they will chase and eat feeder fish I don’t recommend offering them to predatory fish. Store bought feeder fish are kept in terrible conditions and are full of diseases they can pass onto the animal that eats them. They are also poor nutrition since they are fed poor quality food; fresh or frozen fish from your grocery store are much better for your carnivorous fish!

How Often Should I Feed My Jack Dempsey?

When younger, Jack Dempseys grow quite quickly and eat ravenously. Feeding them two or three times per day is best until they reach sexual maturity (4 to 5 inches). After this point their growth rate tapers off and they need less food. You can reduce feedings to once or twice per day at this point!

Breeding Your Jack Dempsey

How Can I Condition Jack Dempseys to Spawn?

Clean water, a spacious aquarium, a variety of protein-rich foods, and a good mate are all that is required. Jack Dempseys can be a little picky when choosing a partner so raising a group of 6 young fish to allow them to pair off naturally is the best way to succeed.

How Can I Tell if a Jack Dempsey is Pregnant?

Once you have a pair eager to spawn their sexual organs will descend and they will spend most of their time around one another. They will likely start digging far more in order to prepare a place to spawn. Unfortunately, keeping live plants with breeding Jack Dempseys is next to impossible. The female will also visibly swell as she starts sproducting eggs – now is a good time to give her extra fat when feeding from sources like earthworms!

Like most cichlids Jack Dempseys are devoted parents. However they will take their aggression out on any other fish in the tank unless your aquarium is quite large. So you may need to either move the tank mates or move the couple to keep them from killing your other fish!

Frequently Asked Questions

How Aggressive are Jack Dempseys?
Jack Dempseys are semi-aggressive; meaner than peaceful community fish but not as aggressive as some other cichlids!

What are Electric Blue Jack Dempseys?
Electric Blue Dempseys are a captive bred color morph entirely covered in bright blue scales. They are a little more sensitive than a standard Dempsey but even more beautiful!

How Big of a Tank Does a Jack Dempsey Need?
An adult Jack Dempsey needs at least 55 gallons of space!


No comments

Leave a comment