Cichlids are a common sight in tropical aquariums. They come in all shapes and sizes, each with its own behaviors and personality.
Jack Dempseys are one of the most well-known cichlids.
They are infamous for their aggression and don’t play well with others, but that does not mean they can’t be kept in groups, or even with other species.
Those who know how to handle their aggressive nature can create a thriving aquarium, but those that don’t will struggle to stop them from harassing their tank mates. When kept properly, this carnivorous fish introduces various colors and plenty of activity to your tank.
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Jack Dempsey Fish Facts & Overview
|Color Form:||Gray with bright flecks|
|Minimum Tank Size:||80 gallons|
|Tank Set-Up:||Tropical freshwater|
|Compatibility:||Aggressive fish of a similar size|
Jack Dempsey, or Rocio octofasciata, are fish from the Cichlidae family.
Most cichlids are either from Africa or America. Jack Dempseys are no exception and are found in slow-moving waters across North and Central America, such as Mexico and Honduras. Cichlids have diversified rapidly in these areas.
They have now been established in the warm waters of Australia and Thailand, where it’s known locally as the Mexican Blue Frontosa.
This carnivorous fish usually lives up to 8-10 years but can survive until 15 years old if kept in a healthy environment.
Most pet stores sell them for $5-10 – rarer varieties can cost a bit more though.
It might be a little harder to find a particular color if you have a specific variety in mind.
Many people are put off by the aggressive nature of this species. Those not used to keeping aggressive fish might struggle to care for them properly, so they are not recommended for beginners.
They tend to be less aggressive in well populated tanks because it’s harder for them to single out and pick on stray fish.
A male will try to establish a territory and will fend off other individuals. If you have plenty of caves and crevices to form different territories, there will be few territory disputes.
They spend a lot of time hiding away in these caves so can appear quite shy. Mostly they will stay in the middle and lower levels of the tank.
Their common name is based on their appearance. They have strong facial features and aggressive nature, similar to that of the 1920s boxer Jack Dempsey.
This species has a large oval body, with long fins. Males will be larger with longer fins.
Their popularity is partly due to the range of colors you can find them in. There are lots of varieties, but the most popular are golds, blues, and pinks.
Color will vary from individual to individual, especially since their color changes as they age. Younger fish are a pale gray with green flecks, older fish become a dark purple-gray with bright blue-green flecks.
Colors can change temporarily – they get pale when they are stressed and dark while mating. You can look at their fins to sex them. Males have long dorsal and anal fins with pointed tips, females have shorter fins that are less pronounced.
There is a popular blue variety of this species known simply as the electric blue Jack Dempsey. This variety is slightly smaller and less aggressive.
Jack Dempsey Fish Size
Your Jack Dempsey fish will grow between 10-15 inches, with females growing a little shorter.
Habitat and Tank Conditions
In the wild you will find Jack Dempsey fish living in a range of slow-moving freshwaters. This includes murky rivers, canals, lakes, and swampy areas.
They prefer tropical climates, so they are used to warm waters. The environment would be slightly acidic with low light levels.
Their surroundings would be a sandy, muddy substrate with rocks and debris sat on top. Plants would be dispersed around too.
Starting at the bottom of the tank, pick a soft sandy substrate since Jack Dempseys spends lots of their time in the lower levels of the water.
When adding decorations, make sure you have multiple caves spread around the tank so that your fish can find and claim their own territories.
You can add plants too as they don’t usually destroy them. However you might find that one day they decide they do not like the plants in the tank and have destroyed them. Be careful to check that any other species you keep won’t destroy them either.
They will need a heater to maintain a temperature between 72-86°F. The pH should be 6-7 and water hardness should be 9-20 dGH.
An air or water pump is not needed because they prefer slow-moving waters, you will just need a filter to create a slight current.
Avoid bright lights or your Jack Dempseys will just hideaway. Their natural water would be slightly murky so use some dimmer lights. Floating plants (like hornwort) can be used to shade certain areas.
What Size Aquarium Do They Need?
Keeping them in a big enough tank is important as a small tank will provoke their territorial tendencies.
Jack Dempsey fish need at least an 80-gallon tank.
How Many Can Be Kept Per Gallon?
Each fish will need at least 55 gallons of water, but they will appreciate more space.
Remember these fish are aggressive and need their own territory so give them each a spot to hideaway.
The aggressive nature of Jack Dempseys can be quite restrictive when looking for tank mates, but that does not mean there aren’t some good options out there.
Tankmates generally need to be a similar size with the same aggressive temperament. This means that no fish can fit in another’s mouth, and everyone can defend themselves.
Peaceful species will be harassed, possibly to the point of death. Small fish like tetras will just be treated as food.
Invertebrates like shrimp and snails are popular in tropical aquariums, but they will likely be viewed as a snack.
Can You Keep Jack Dempsey Fish Together?
Keeping Jack Dempseys together in a species-only tank is the best option for beginners. It can be hard to keep other species alive.
Just remember males don’t tolerate other males very well, so one per tank is the safest option.
Jack Dempseys have simple care requirements. The problems start when you keep a group or mix them with other species.
Handling their aggression can be difficult if you haven’t kept aggressive cichlids before. If cared for poorly, your Jack Dempseys will start harassing each other and other species.
This species is not the best option for newcomers to fishkeeping.
If the aggression is handled properly, it is not difficult to keep them healthy. However, they can get diseases just like all other freshwater fish. One of the most common issues is Ich (white spot disease) – this is an ectoparasite that appears as white nodules on the body and fins.
Raising the water temperature in your tank to 86°F can help to treat the disease.
Another common disease is Head and Lateral Line Erosion (HLLE). This forms pits or cavities on the head. It is usually caused by poor nutrition, so you will need to change their diet if you spot it.
An unhealthy environment usually promotes disease, so you need to keep the tank clean. Anything you add to an established tank can bring disease with it so quarantining things is a must.
Diet and Feeding
As carnivorous fish, a Jack Dempsey’s diet would normally consist of anything meaty that they can fit into their mouths. They can quickly grab worms, crustaceans, insects, and small fish.
There are many options for feeding them in a home aquarium. They are not picky eaters so you can choose what is easiest for you.
Processed dried foods are generally cheaper and readily available. You can find pellets and flakes designed specifically for cichlids. If you are going to use processed foods, pick some additional frozen/live foods to add into the tank occasionally – this will help give them a range of nutrients.
Popular options include bloodworms and brine shrimps. Larger insects like crickets, grasshoppers, and fruit flies will go down very well with your Jack Dempseys.
Herbivorous foods will mostly be rejected, which is why you can keep plants in the tank with a low risk of them being eaten.
Feed your adults 1-2 times a day. Add an amount that they can finish within two minutes. Juveniles should be fed a bit more often, 2-3 times a day, to help them grow.
When a pair of Jack Dempseys are ready to mate their colors will darken. If the male is ready to mate but the female is not, she may be harassed to the point of death.
Conditions need to be near perfect for spawning to be initiated. The water needs to be clean and within the parameters outlined earlier. A temperature at the higher end of the range (~84°F) is a good trigger.
Larger males will be more successful in seducing a female (this is common for many cichlids).
Once mating has occurred, up to 500 eggs can be produced. The eggs are attached to a nearby flat surface such as decorations, the substrate, or the walls of the aquarium. After three days they should have hatched.
The parents are quite attentive to the fry, they dig holes in the substrate to protect the fry until they are free-swimming. Both the mother and father will share the duty of guarding the young.
They even crush up food and release it for the young to eat until they are big enough to find food themselves.
If the parents are stressed by poor environmental conditions, they might start eating the young and will need to be separated.
Are Jack Dempsey Fish Right For Your Aquarium?
Every aquarium is different, but most established tanks won’t be able to house a new group of Jack Dempseys. This cichlid will need a tank designed especially for them.
This is mainly due to their aggressive nature and the restriction this creates on tank mates. It is not a fussy species, so as far as setting up the tank goes, they are relatively simple to provide for.
They are also not fussy about their diet either and will accept most of the same foods as other carnivorous cichlids.
Beginners may struggle to keep these fish, but if you manage it you will be left with some colorful fish with big personalities.
Do you keep Jack Dempseys in a community aquarium? Let us know about your setup in the comments section below…