Differences Between Male And Female Jack Dempsey Fish

Differences Between Male And Female Jack Dempsey Fish

Male and female Jack Dempsey fish

Jack Dempsey fish are popular with fishkeepers because of their bright coloration, strong build, and aggressive attitude. However, determining their gender can be difficult for aquarists.

This little guide outlines the subtle differences between the male and female Jack Dempsey fish.

Physical Differences Between Male And Female Jack Dempsey Fish

Jack Dempsey fish got this name because of their ferocious appearance and aggressive nature.

These characteristics resemble the American boxer William “Jack” Dempsey Harrison.

The physical differences are subtle in young Jack Dempsey fish and become more prominent when they reach adulthood.

Given below are some of the physical differences between an adult male and female Jack Dempsey fish.


Jack Dempsey fish have large oval bodies.

However, a male Jack Dempsey fish is typically bigger than the female with a more elongated body shape.

In captivity, the average size of a male Jack Dempsey fish is around 10 inches in length, and that of a female is 8 inches in length once they grow fully.


Male Jack Dempsey fish have a bright color that seems to change when viewed from different angles.

In contrast, female Jack Dempsey fish can be distinguished by their dull or pale coloration.

Cheek Markings

Male Jack Dempsey fish have blue spots directly behind their eyes and no spots near the mouth on the lower part of their cheeks.

On the contrary, markings on females reach the entire length of the cheeks with large iridescent spots on the lowest part of their faces.

Tail Fin

Male Jack Dempsey fish have pointed edges on their tail fin.

In contrast, female Jack Dempsey fish have rounded edges on their tail fin.

Dorsal Fin

The dorsal fin of a male Jack Dempsey fish is longer and has sharper ends.

On the other hand, the dorsal fin of a female Jack Dempsey fish is rounded.

Nuchal Hump

Male Jack Dempsey fish can get a nuchal hump when they mature, while females can’t.

Behavioral Differences Between Male And Female Jack Dempsey Fish

The male and female Jack Dempsey fish have some noticeable behavioral differences, as mentioned below.


Male Jack Dempsey fish flare their gills to communicate anger or aggression to other males.

In contrast, the female fish don’t often show aggression but can flare their gills to indicate superiority or dominance.


Aggressive Jack Dempsey fish

Male Jack Dempsey fish are known to get more aggressive toward other males, even before they mature fully.

So it’s not best to keep two males together.

The adult male Jack Dempsey fish are intolerant toward their male species.

In worst cases, they will fight each other until one fish succumbs to injuries from such unwarranted aggression.

On the other hand, keeping a few female Jack Dempsey fish together is safe.

Going by the recommended rule, you can add one male fish for every 3 or 4 females.

Most female Jack Dempsey fish also become aggressive during breeding when they try to protect their eggs or young ones from other tankmates.


Jack Dempsey fish are fierce and aggressive.

However, males are vicious and known to chase, bite, or bully small or vulnerable fish without any particular reason.

Unlike males, female Jack Dempsey fish aren’t as vicious and fierce in their behavior and can get along in tanks containing other fish species.


Male Jack Dempsey fish are more territorial than females and will often chase away any fish that invades their territory.

On the other hand, females aren’t highly territorial and can coexist with other female Jack Dempsey fish or other fish species.

Wild Vs. Domesticated Jack Dempsey

Given below are a few differences between wild and domesticated Jack Dempsey fish.


In their natural habitat, Jack Dempsey fish can grow up to 15 inches in length.

Typically, the males grow bigger compared to females.

When kept in captivity, the average size for males is around 10 inches, while females are around 8 inches long once they reach full maturity.

Tank size is a vital factor that can significantly contribute to their growth.

A large aquarium will assist these fish in reaching their full growth potential, while a small tank can stunt their growth.


Jack Dempsey fish have an average lifespan of 8 to 10 years in captivity.

However, these fish are known to live longer, between 12 to 15 years, in their natural environment.

In the wild, the water conditions are stable, and their food resources are abundant and varied, providing them with the required nourishment to improve their longevity.

However, in a captive environment, the tank setup and water conditions depend entirely on the fishkeeper.

Any negligence adversely affects their lifespan.


Jack Dempsey fish are more inclined toward a carnivorous diet and like to devour insects, worms, larvae, mollusks, crustaceans, and small fish in their natural habitat.

This diet offers them the required nutrition and stimulates faster growth.

However, in captivity, they’re entirely dependent on the food provided by the fish owner.

Therefore, feeding Jack Dempsey fish with a protein-rich and well-balanced diet is essential to ensure faster growth and overall well-being.

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