Jack Dempsey Fish

Jack Dempsey Fish Care Guide

In the hobby, this is one of my all-time favorite fish. They’re large and badass, with vibrant colors and engaging personalities.

However, they aren’t for everyone.

I’ll tell you everything you need to know about Jack Dempsey fish in this tutorial so you can decide if they’re perfect for you.

Jack Dempsey Fish Overview

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The Jack Dempsey (Rocio octofasciata) is a cichlid found in Mexico, Belize, Guatemala, and Honduras’ freshwater streams and rivers.

In the United States, Australia, and portions of Asia, there are established populations. In these regions, it is considered an invasive species, and it was most likely introduced when aquarists released their pets into the wild.

What do Jack Dempsey fish look like?

Jack Dempsey as an adult is really gorgeous.

They are oval-shaped fish with enormous dorsal and anal fins and a large rounded tail. They are longer than they are tall.

The hue of their base ranges from a dusky, rosy pink to a dark, almost black tone.

Metallic, iridescent blue/green spangles adorn them, making them highly eye-catching. As the fish moves, these spots reflect light and flash brightly.

One of my favorite species has always been Dempseys. They glisten and sparkle in a way that looks almost impossible as if something so wonderful couldn’t possibly be natural.

Then there are captive-bred color variations like electric blue Jack Dempseys, which have even greater areas of iridescent blue/green. They nearly appear to be a different species of fish altogether.

The iridescent spangles become more apparent as the fish grows older and larger.

They are a showpiece species that can be seen from across the room since they grow to be quite enormous fish.

For decades, their size, color, and tenacious personalities have made them popular in the hobby.

How big do they get?

Big. Really, really enormous. Males reach a maximum height of 12 inches (30 cm) in the wild, while females reach a maximum height of roughly 10 inches (25 centimeters).

Males may grow up to 10 inches in length while females can grow up to 8 inches in length if provided ample space in an aquarium (20 centimeters).

Pro Tip: If you don’t put your fish in a big enough tank, they won’t grow to their full size. Their growth will be stunted if they are housed in a smaller tank. When it comes to aquariums, remember that bigger is always better.

Dempseys are not just long, but also thick-bodied and hefty fish. So a 6 inch Dempsey has a far larger bioload (the quantity of waste that enters the water) than a 6-inch silver dollar.

When deciding on tank size and filtration levels, keep this in mind. Both of these will be discussed later in the article.

What is their life expectancy?

Dempseys can live for 10 to 15 years, so keep in mind that bringing one home is a long-term commitment.

Jack Dempsey Fish Tank: Preparation and Setup

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Aquarium Size

If you wish to keep this species, be aware that you’ll need a very large tank. As a bare minimum, I would recommend a 55 gallon (208 liters) tank for a single fish.

When it comes to aquariums, bigger is always better, especially when harboring enormous species.

If you want to keep a pair of Dempseys, you’ll need a 100 gallon (378 liters) tank.

If all of this sounds like too much of a commitment for you, consider going with a lesser fish species.



One of the most critical aspects of your aquarium is filtration.

I’ll give you a quick rundown of why this is vital, and how it’s much more necessary when keeping huge fish like Dempseys.

Fish expel waste into the water that surrounds them on a regular basis. And the more they produce, the more waste they generate.

All of your waste sinks to the bottom of your tank, where it begins to decompose and emit ammonia (NH3). This is problematic since even trace amounts of ammonia are poisonous to fish and invertebrates.

Beneficial bacteria live in our filters, which is fortunate for us fishkeepers. One type consumes ammonia and converts it to nitrite (NO2 -1), a harmful byproduct. However, another kind of bacterium quickly consumes the nitrite and produces nitrate (NO3-).

The nitrogen cycle in aquariums is the name given to this entire process.

Nitrate, on the other hand, is far less hazardous and can be allowed to accumulate in the aquarium between water changes.

Pro Tip: In a fresh tank, getting the nitrogen cycle up and going takes time. Check out our methods for doing a fishless cycle for more information on how to prepare your tank ready for fish.

However, you’ll need a filter that can handle all of that garbage. The filter must be large enough to hold a sufficient number of helpful microorganisms. You’ll have enough bacteria to consume all of the ammonia created by a massive fish this way.

It must also be able to pump enough water to allow dissolved wastes to touch the bacteria.

There aren’t enough bacteria on hand to cope with all the excrement without a large enough filter. Then, as decomposing garbage breaks down in the tank, lethal ammonia is released, rendering the water unlivable.

And there are a lot of Jack Dempseys. As a result, they generate enormous volumes of garbage.

I strongly advise you to use a larger filter to match your colossal fish and its colossal feces.

I also don’t believe there is such a thing as too much filtration. So choose a filter that can easily handle your tank’s volume and then some.

You may even add some more filtration by using a sponge filter.


The natural habitat of the Jack Dempsey fish stretches from Mexico to Honduras, and it is found in fairly warm conditions.

For these large men, a heater is an absolute must.

It’s preferable to go with a somewhat larger heater than a smaller one. A small heater will struggle to keep the water warm enough all of the time. To keep the temperature stable, it will have to be turned on virtually continually.

This, I’ve discovered, drastically reduces the lifespan of a heater.

You want them to endure as long as possible because they’re one of the more expensive pieces of equipment in your tank.

Plants, Substrate, and Decor


So, if you’re looking for a fish to go in a big, gorgeous planted tank, this isn’t the fish for you. Like many cichlids, Jack Dempsey fish enjoy digging in the substrate.

After a water change, I prefer to balance out the gravel so it appears nice and even. I once observed a Dempsey I owned spend hours digging out a pit and filling it with gravel. He’d dug out more than half of the tank by the end of the day.

Some owners are unconcerned with Dempseys chewing up plants, while others believe it is the fish’s life goal.

There’s also no way of knowing what kind of fish you’ll get.

They don’t eat the plants as a serum does, but when they wish to rearrange the tank, they dig them up and drag them away.

They won’t eat floating plants like hornwort, water sprite, pennywort, frogbit, or water lettuce, but they’ll eat anything rooted in the substrate.

Best Aquarium Plants is a related article.


I would recommend either sand or gravel for Dempseys.

Because they prefer to dig, a planted dirt substrate would be a massive mess because they’d break it apart.

They also look better against a dark background, in my opinion.

They’ll change their hue to blend seamlessly with the environment. As a result, rather than being a washed-out purple/pink, their base hue becomes very dark, nearly black.

Their iridescent spangles stand out even more as a result.

To help your fish darken, I propose a dark brown or black substrate.

It’s also recommended to use an inert substrate. Substrates labeled “cichlid sand” should not be used.

Aragonite, a crystallized type of calcium carbonate, is used to make cichlid sand (CaCO3). I don’t want to bore you with a chemistry lesson right now. To summarise, aragonite sands continuously leach calcium carbonate into your water, increasing the hardness and pH of the water.

The higher mineral levels are ideal for African cichlids that need hard water, but not so much for soft water cichlids like Jack Dempseys.

For Central and South American cichlids, it’s best to use inert sand.


Open swimming spaces and huge pieces of decor that they may use to establish a territory and hide are required for Jack Dempsey fish.

They certainly like having a large tunnel to retreat to when they are in danger.

Large boulders or driftwood that they can hide behind once they’ve grown to full-size offer suitable hiding sites. When he was terrified, mine would hide behind some large rock work I had in the tank.

Jack Dempsey Fish Ideal Water Parameters

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This fish’s native waters are extremely soft and have an acidic pH.

However, because Jack Dempsey fish are tank-bred, they may adapt to a variety of water conditions.

  • Temperature: 74°-85°F (23°-29°C)
  • Ammonia/Nitrite: 0
  • Nitrate: <40 ppm
  • pH: 6.0-7.0
  • GH: 3-8 dGH (50-133 ppm)
  • KH: 4-6 dGH (72-107 ppm)

Tank Mates and Temperament

In most community tanks, Jack Dempsey fish isn’t the best choice.

They can be violent, and as they become older, they tend to grow more territorial. They’re also large enough to bother and kill most other fish.

Dempseys frequently establish territory in a cave or behind some driftwood so that they have a safe haven if they are attacked.

They’ll keep an eye on the area and try to scare away any fish that get too close.

They remind me of the stereotyped tough dudes that stand on the corner and defend their land in movies.

In a large enough tank, a mated pair can be kept together. They might still beat each other up now and then, but for the most part, they’ll just hang out together happily.

Mated pairs will not tolerate other fish in the aquarium while they are reproducing, so keep that in mind. They will annihilate other fish with a vengeance. A breeding pair should be kept in their own tank.

However, it is impossible to maintain two sexually mature guys together. They will continue to battle until one or both of them is killed.

This isn’t simply applicable to Dempseys. Most of the large Central and South American cichlid species fall within this category. In the wild, each male would establish a territory and chase away any other male who approached.

The only way to keep Dempseys in a community tank is to mix them with other species that have similar adult sizes and degrees of aggression, such as green terrors, fire mouths, or serums.

However, a large tank, such as 150 gallons, will be required to complete this task (568 liters). If the Dempsey becomes overcrowded, it will most likely begin to kill other fish.

Smaller fish species should be avoided at all costs. Anything a Dempsey can fit into its mouth will almost certainly become a snack.

Smaller fish are frequently harassed and killed by Jack Demsey fish, even if they aren’t tiny enough to be eaten.

Feeding and Diet Requirements

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Carnivores, Dempseys pursue live prey in the wild. This means that a diversified, high-animal-protein diet is essential.

What kind of food should I give my Jack Dempsey cichlid?

Dempsey’s diet should consist primarily of high-quality pelleted food.

Omega One Cichlid Pellets and Fluval Bug Bites Cichlid Formula are two of my favorite fish foods. Both foods contain a lot of high-quality protein.

The pellets are also large enough that larger, adult fish can easily eat them.

Additionally, a variety of live and frozen meals, such as bloodworms, blackworms, daphnia, and brine shrimp, should be offered to these fish to fill out their diet.

How often should I feed my Jack Dempsey cichlid?

To help young Jack Dempseys grow, feed them 2-3 little meals per day.

Adults should be fed once or twice each day.

It’s crucial not to overfeed them, so only give them as much food as they’ll eat in about 2 minutes and remove any uneaten food right away.

Are Jack Dempsey Fish Right For You?

In the hobby, this is one of my all-time favorite fish. They’re large and badass, with vibrant colors and engaging personalities.

However, they aren’t for everyone.

Because they are such large fish, it is critical that they have enough room. I wouldn’t put a single Dempsey in anything smaller than a 55-gallon aquarium, even if it’s the only fish in the tank.

I’d recommend at least a 100 gallon (378 liters) tank if you want to keep a couple or have additional large cichlids in the tank.

Because they are so large, they generate a lot of waste and necessitate a tight maintenance schedule to keep their tanks clean and their water safe.

It’s also critical to ensure that you have enough filtration to handle the massive amount of waste this fish will generate.

These gorgeous bruisers aren’t the best community fish. They might be abrasive and possessive.

Other large Central American cichlids are the only tank mates who have a chance, but be prepared to move or re-home fish if this doesn’t work out in the long run.

I definitely recommend these fish if you can offer what they require. They’re incredibly stunning and make wonderful pets.

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