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Can Oscar Fish And Jack Dempsey Fish Live Together?

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Oscar fish and Jack Dempsey, both captivating and visually appealing species, raise the question of whether they can peacefully coexist in the same tank.

Going deeper, what size of tank would be appropriate to house these two species together? What factors should we take into account when arranging the tank and maintaining water conditions?

In this article, I’ll explore these questions and more. Let’s dive right into it.

Can I Keep Oscar Fish And Jack Dempsey Fish Together In The Same Tank?

No, it’s not recommended to keep Oscar fish and Jack Dempsey together in the same tank. However, they can be kept together under very specific conditions, but it’s generally risky.

Here’s why:

  • Size Compatibility: Oscar fish can grow up to 14 inches while Jack Dempseys typically reach 10 inches. The difference in size could lead to territorial disputes or bullying.
  • Aggression Levels: Oscar fish are known for their aggressive behavior, especially when establishing territory. Pairing them with Jack Dempseys can intensify territorial conflicts.
  • Dietary Needs: While both fish are carnivorous, Oscar fish might exhibit predatory behavior. Smaller Jack Dempseys could become potential prey if Oscars become overly aggressive.
  • Tank Space: Both Oscar fish and Jack Dempseys need ample space. Ideally, for a mature Oscar fish, a tank of at least 75 gallons is recommended, and combining with Jack Dempseys means even larger tank requirements.
  • Stress Factors: Introducing different aggressive species like Oscar fish and Jack Dempseys can elevate stress levels in the tank. Stress in fish can lead to illness, color loss, and decreased lifespan.

Also Read: 19 Great Oscar Fish Tank Mates

Oscar Fish vs. Jack Dempsey: Behavior

The first factor worth considering is the Oscars’ and Jack Dempsey’s natural behavior. Here is what you should know:

Oscar Fish: Natural Behavior

Oscar fish are known for their highly interactive and aggressive behaviors. They often dig, rearrange substrate, and can be territorial in nature.

Let’s explore the details:

  • Territorial Nature: Oscar fish tend to be highly territorial, especially during breeding seasons. They will often claim certain areas of the tank and defend them rigorously.
  • Interactive Behavior: Oscars are highly interactive with their owners and even perform “water tricks.” They can recognize their owners and may respond by swimming up to the tank glass.
  • High Energy: Oscar fish are often seen swimming rapidly or engaging in other energetic behaviors. This requires ample tank space and proper environmental enrichment.
  • Digging Habits: Oscars have a tendency to dig in the substrate, rearranging their environment. This can cause issues if delicate plants or other less hardy tank mates are present.
  • Aggressive Feeding: Oscar fish are aggressive eaters that can consume a variety of diets including pellets, live foods, and frozen options. Their aggression extends to feeding times where they dominate food sources.

Jack Dempsey: Natural Behavior

Jack Dempsey fish are also aggressive but tend to be more reclusive and less interactive compared to Oscar fish.

They exhibit strong territorial behavior and are often less sociable with other species. Understanding these traits can help:

  • Less Social: Jack Dempseys are less inclined to interact with owners. Unlike Oscar fish, they may not recognize or swim up to the glass to greet you.
  • Territorial Similarity: Like Oscar fish, Jack Dempseys are highly territorial, but they tend to stick to their chosen corners and defend them quietly.
  • Subdued Energy Levels: Jack Dempseys are less energetic in comparison to Oscar fish. They often prefer hiding spots over open swimming.
  • Substrate Preference: While they also dig and rearrange the substrate, they are less disruptive in their digging habits compared to Oscar fish.
  • Selective Feeding: Jack Dempseys are also carnivorous but are more selective in their food choices. Unlike Oscar fish, they may not rush to the food but rather approach it cautiously.

Ideal Parameters For Oscar Fish And Jack Dempsey Fish

Both Oscar fish and Jack Dempsey require specific water parameters for optimal health. Here’s a comparison of their ideal parameters:

ParameterOscar FishJack DempseyBoth Types
Temperature74°F to 81°F72°F to 86°F74°F to 86°F
pH Level6.0 – 7.56.5 – 8.06.0 – 8.0
Water Hardness5 – 20 dGH10 – 15 dGH5 – 15 dGH

Oscar Fish: Ideal Parameters

Oscar fish thrive best in specific water conditions that emulate their natural tropical environments.

Ensuring the right parameters is vital for the health and well-being of Oscar fish. To delve deeper:

  • Temperature: Oscar fish prefer warmer waters, with temperatures ranging from 74°F to 81°F (23°C to 27°C). Maintaining this range ensures optimal metabolic and digestive processes.
  • pH Level: The ideal pH level for Oscar fish is between 6.0 and 8.0. This neutral to slightly alkaline range replicates their natural freshwater habitats.
  • Water Hardness: Oscar fish are tolerant of a range of hardness, but ideally, it should be between 5 and 20 dH. Consistent water hardness aids in maintaining stable pH levels.

Also Read: Can Oscar Fish And Blood Parrot Cichlids Live Together?

Jack Dempsey: Ideal Parameters

Jack Dempsey fish, originating from Central America, require distinct water parameters to mirror their natural habitats.

Properly maintaining these conditions ensures longevity and vibrant health for Jack Dempseys. Here are the specifics:

  • Temperature: Jack Dempsey fish thrive in temperatures between 72°F and 86°F (22°C to 30°C). Consistent temperature within this range promotes healthy growth and behavior.
  • pH Level: The recommended pH level for Jack Dempsey fish is between 6.5 and 8.0. This ensures an environment that mimics their natural freshwater setting.
  • Water Hardness: Jack Dempseys prefer a water hardness between 6 and 20 dH. Maintaining this range helps in providing a stable environment and optimal health.

Oscar Fish vs. Jack Dempsey: Tank Setup

Oscar fish and Jack Dempsey have distinct tank setup preferences. Here’s a guide to setting up a tank for each fish type, and considerations for a tank housing both:

Setup CriteriaOscar FishJack DempseyBoth Types
Ammonia, Nitrite & Nitrate0 ppm ammonia/nitrite, <40 ppm nitrate0 ppm ammonia/nitrite, <40 ppm nitrate0 ppm ammonia/nitrite, <40 ppm nitrate
Tank SizeAt least 75 gallonsAt least 55 gallonsAt least 125 gallons or larger
FoliageHardy plants like java fernDense plants and driftwoodCombination of both types
DecorationsLarge, heavy decorationsCaves or large rocksCombination ensuring ample hiding spots
FilterPowerful canister filterRobust filter (canister/HOB)High-quality canister filter
HeaterSubmersible heaterReliable aquarium heaterSubmersible heater covering full range
SaltSmall amountsSmall amountsSmall amounts, beneficial for both
PumpStrong water pumpQuality pumpStrong pump ensuring good circulation
LightingModerate LED lightingModerate, indirect lightingModerate LED with indirect brightness

Oscar Fish: Ideal Tank Setup

Oscar fish are large, energetic, and have specific requirements to ensure they live a healthy life.

To replicate their natural habitat and maintain optimal conditions, it’s crucial to set up the tank appropriately for Oscar fish. Breaking it down:

  • Ammonia, Nitrite & Nitrate: Oscar fish need water with 0 ppm ammonia and nitrite, and below 40 ppm nitrate. Regular water changes and a good filtration system can maintain these levels.
  • Tank Size: Due to their size and activity, Oscars require at least a 75-gallon tank for one adult. Bigger is always better for these active swimmers.
  • Foliage: Oscar fish may uproot plants, but hardy species like java fern can be tried. Ensure the plants are anchored properly.
  • Decorations: Oscars are curious and tend to move things, so large, heavy decorations are ideal. Avoid sharp edges that can harm the fish.
  • Filter: A powerful canister filter is essential for Oscar fish. It should handle the high waste output and provide adequate water circulation.
  • Heater: Oscars prefer warmer waters. A submersible heater that can maintain the tank between 74°F to 81°F is ideal.
  • Salt: While not mandatory, aquarium salt can be beneficial for Oscars in small amounts. It can help in stress reduction and fight minor infections.
  • Pump: A strong water pump helps in circulation and oxygenation. Ensure the flow isn’t too strong to disturb the Oscar fish.
  • Lighting: Moderate lighting is preferred for Oscar fish. LED aquarium lights on a timer can replicate a natural day-night cycle.

Jack Dempsey: Ideal Tank Setup

Jack Dempsey fish are less active than Oscar fish but still require specific conditions for a thriving environment.

A suitable tank setup can make a big difference in the behavior and health of Jack Dempseys.

Here’s a closer look:

  • Ammonia, Nitrite & Nitrate: Jack Dempseys also require 0 ppm ammonia and nitrite, and nitrates should be kept below 40 ppm. Weekly testing and water changes are necessary.
  • Tank Size: An adult Jack Dempsey needs at least a 55-gallon tank. However, for pairs or more fish, a larger tank is advised.
  • Foliage: Jack Dempseys enjoy hiding, so dense plants and driftwood are recommended. Plants provide both shelter and breeding sites.
  • Decorations: They love hiding spots. Caves or large rocks can offer them refuge and reduce stress.
  • Filter: A robust filter that can handle bioload and circulate the water effectively is necessary. Canister or HOB filters work well.
  • Heater: Maintaining a temperature range between 72°F and 86°F is vital. A reliable aquarium heater is crucial for this.
  • Salt: Like Oscar fish, small amounts of aquarium salt can be beneficial for Jack Dempseys. It offers therapeutic benefits.
  • Pump: Good water circulation is vital. A quality pump ensures oxygenation and helps in distributing heat evenly.
  • Lighting: Jack Dempseys are less picky about lighting but moderate, indirect lighting is ideal. Ensure there’s no extreme brightness or darkness.

Also Read: Can Oscar Fish And Flowerhorns Live Together?

The Dietary Requirements Of Oscar Fish And Jack Dempsey Fish

A varied and balanced diet is essential for both Oscar fish and Jack Dempsey. This table provides a snapshot of their dietary needs and considerations for a tank housing both:

Dietary CriteriaOscar FishJack DempseyBoth Types
Food TypesLive foods, frozen foods, pelletsLive foods, frozen foods, pelletsVaried diet of live and frozen foods, pellets
QuantityConsumed within 2-3 minutesConsumed within 2 minutesCareful portioning to avoid overfeeding
Feeding ScheduleOnce or twice a day (adult)Once a day (adult)Separate feeding zones and consistent schedule

Oscar Fish: Ideal Dietary Requirements

Oscar fish are carnivorous by nature and require a diverse, protein-rich diet for optimal health and growth.

Their diet should closely resemble what they would consume in their natural habitat to ensure they get the required nutrients.

Diving into specifics:

  • Food Types: Oscars primarily thrive on a diet of live foods, frozen foods, and high-quality pellets. Common choices include crickets, mealworms, and specially formulated Oscar fish pellets.
  • Quantity: Oscar fish are voracious eaters, but overfeeding should be avoided. Feed an amount they can consume within 2-3 minutes, ensuring no leftover food.
  • Feeding Schedule: It’s best to feed adult Oscar fish once or twice a day. For juveniles, more frequent feedings (2-3 times a day) can support their rapid growth.

Jack Dempsey: Ideal Dietary Requirements

Jack Dempsey fish are also carnivorous, but they have slightly different preferences and dietary requirements compared to Oscar fish.

A balanced and varied diet is vital for their overall well-being. Detailing their diet:

  • Food Types: Jack Dempseys prefer a mix of live foods, frozen foods, and carnivorous pellets. Bloodworms, brine shrimp, and formulated pellets are typical choices for these fish.
  • Quantity: It’s important not to overfeed Jack Dempseys. A quantity that can be consumed in 2 minutes is a general guideline to follow.
  • Feeding Schedule: Adult Jack Dempseys should be fed once a day. However, juveniles can benefit from 2 daily feedings to support their growth.

Tips for Keeping Oscar Fish with Jack Dempsey Fish

Keeping Oscar fish with Jack Dempsey can be a challenging endeavor due to their territorial and aggressive natures.

However, with the right considerations and preparations, it is possible to house these two species together in harmony.

Here’s how to make cohabitation successful:

  • Tank Size: Ensure a large tank, preferably at least 125 gallons or larger. This provides ample space for territories and reduces aggression.
  • Tank Dividers: Consider using tank dividers or barriers during the initial introduction. This allows both Oscar fish and Jack Dempsey to establish territories without direct confrontation.
  • Introduce Together: Adding the Oscar fish and Jack Dempsey simultaneously can reduce territorial conflicts. This stops one fish from dominating the tank before introducing the other.
  • Offer Shelter: Include sufficient caves, stones, and driftwood. Both fish appreciate these refuges, which can mitigate stress and hostility.
  • Watch for Aggressiveness: Closely monitor any signs of aggression. If the Oscar fish or Jack Dempsey gets overly hostile, think about a temporary separation.
  • Designated Feeding Areas: Create specific feeding zones for each fish. This lessens food competition and the likelihood of disputes during meal times.
  • Consistent Checks: Regularly check water conditions because waste from both Oscar and Jack Dempsey can build up fast. Keeping the water at its best can lower stress and hostility.

Should I Opt for an Oscar Fish or a Jack Dempsey?

Choosing between an Oscar fish and a Jack Dempsey largely hinges on what you personally prefer and the type of aquarium journey you desire.

Both have their own charm, yet they present different care challenges and temperaments. Important aspects to note:

  • Tank Capacity: Oscars generally need more spacious tanks due to their activity and size. One mature Oscar needs at least a 75-gallon tank, whereas a Jack Dempsey can thrive in a 55-gallon one.
  • Nature and Interaction: Oscars are typically more engaging and often seen as more “pet-like”. On the other hand, Jack Dempseys display a spirited character and may exhibit greater territorial tendencies.
  • Feeding Patterns: Both are meat-eaters, but Oscars might need a broader range of live foods, making their feeding regimen potentially pricier and more intricate than the Jack Dempsey’s.
  • Care Intensity: Oscars tend to be messier, leading to regular water replacements and stronger filtration. Jack Dempseys are somewhat less demanding here.
  • Visual Appeal: Both are undoubtedly captivating. However, Oscars boast a broader range of designs and hues, while Jack Dempseys shimmer in lovely blue or purple, but with a more consistent look.


For the skim-readers, here’s a quick rundown:

  • Housing Oscar fish and Jack Dempsey in one tank isn’t usually advised due to possible issues and altercations.
  • Size differences might provoke territorial clashes and intimidation, with the combative nature of both fish exacerbating disputes.
  • The predatory tendencies of Oscar fish could put smaller Jack Dempseys at risk, and stress from sharing a space might lead to sickness and shorter life spans.
  • Each fish possesses distinct behaviors: Oscars are interactive, territorial, and vivacious, whereas Jack Dempseys are somewhat reserved, also territorial, but less lively.
  • Ensuring appropriate tank arrangements, water quality, and feeding is crucial for the welfare of both fish species.