Oscar Fish Tank: The Oscar Tank Setup Guide

Oscar Fish Tank
Oscar Fish Tank

How to Setup an Oscar Fish Tank

Welcome to the fascinating world of Oscar fish, a species that hails from the diverse and vibrant ecosystems of the Amazon River. Their native habitat is a testament to their unique needs and preferences when it comes to tank setup. This article will guide you through the process of setting up an Oscar fish tank, providing design ideas inspired by their origin. We’ll delve into creating a well designed planted Oscar tank that not only meets the needs of these magnificent creatures, but also brings a piece of the Amazon right into your living room.

Tank Size

Oscar fish are large, active, and intelligent fish. Therefore, it is important that they are placed in a tank of adequate size. Here are some tank size requirements to consider:

  • For 1 Oscar Fish: The minimum tank size for a single Oscar fish is a 55-gallon tank. With that said, the ideal tank size would be 75 gallons or larger. This is because Oscars can grow very large, well over 12 inches long, and they need plenty of space to swim and explore.
  • For 2 Oscar Fish: If you plan to keep two Oscar fish together, it will require a larger tank. The minimum recommended tank size for two Oscars is at least a 75-gallon tank. With that said, the ideal tank size would be 100 gallons or larger. This allows each fish enough space to establish its own territory and helps reduce potential aggression.
  • For 3 Oscar Fish: For three Oscar fish, the recommended minimum tank size is at least 100 gallons. With that said, the ideal tank size would be 125 gallons or larger. This ensures that each Oscar has ample space to grow and move around comfortably.

As a general rule of thumb, there should be approximately 30 gallons for each additional Oscar fish.

If the tank is too small, it may cause stress, aggression, and overall poor health. Therefore, it is important that there is enough space for all fish. Having an adequate tank size would be the foundation to a good Oscar tank setup.

How many Oscar fish should be kept together?

Oscar fish can live alone. They are capable of thriving without the presence of other fish companions. However, sometimes they may get depressed being lonely, and become inactive. Therefore, adding other Oscar fish may keep them happy.

With that said, due to their large size and aggressive tendencies, it can be a challenge to add multiple Oscar fish in one tank. Having adequate space in the tank, as well as plenty of hiding places may help multiple Oscars to coexist. However, each Oscar fish is different, so things can go wrong even with a good tank setup. Therefore, having a backup plan would be necessary. A second tank or tank separator may be needed if the fish become overly aggressive.

Tank Setup

Creating the perfect environment for your Oscar Fish involves more than just filling a tank with water. It’s about replicating their natural habitat to provide them with the most comfortable living conditions. This includes maintaining the right temperature, ensuring optimal water parameters, installing an efficient filtration system, and providing appropriate lighting. The substrate should be carefully chosen, and elements like driftwood and rocks can be added for a more natural feel. Aquarium plants can provide additional cover and contribute to a healthy ecosystem, while decor items can add a touch of personality to your Oscar tank setup.

Temperature & Water Parameters

The temperature and water parameters for an Oscar fish tank are as follows:

  • Temperature: The best temperature for Oscar fish is between 75 and 80 degrees Fahrenheit (23 – 27°C).
  • pH: They prefer a pH balance of between 6 and 8.
  • Water Hardness: Oscars can tolerate a wide range of water hardness levels but it is recommended to keep it around 12dH – 15dH.

Regarding ammonia, nitrite, and nitrate, these compounds should be as low as possible. For Oscar fish, ammonia and nitrite should be 0 ppm, while nitrates should be kept below 20 ppm1.

Please note that these are general guidelines and individual fish may have slightly different requirements. Always monitor your fish’s behavior and health to ensure they are comfortable in their environment. If you notice any changes or warning signs, you may need to adjust the water parameters accordingly.

Filtration System

Oscar fish require a good filtration system in their tank. It’s recommended to use a filter that can accommodate the water volume, provide adequate oxygenation, and maintain water quality. Depending on the size of the aquarium, it is best to use a filter with a capacity of at least 2 times the tank’s capacity. Since a capable filter is needed, canister filters are recommended for most Oscar tanks.

As for the current, Oscar fish do like it. In their natural habitat in the Amazon basin, they are often found in areas with a strong current. Therefore, your filter should be able to produce a strong current in your tank. However, it’s worth noting that while Oscars in the wild inhabit areas with strong currents, they also tend to inhabit shallow, slow-moving waters. Thus, in a home aquarium, having an aquarium with an adjustable flow rate would be ideal. 


Oscar fish do require an aquarium light in their tank. This helps them to find food easier and better navigate their surroundings. However, they shouldn’t be kept in direct sunlight and prefer a dimly lit environment. Ideally, you should provide about 10-12 hours of light a day. Please keep in mind that excess light can cause algae in your fish tank. Standard aquarium lighting will be sufficient. LED lighting with an adjustable brightness option and/or a blue light feature is also a good choice, as it will help display the Oscars’ colors very well.


The recommended substrate for Oscar fish tanks is either gravel or sand. Oscar fish are known to be intelligent and will often ‘redesign’ their environment to suit their liking. They typically move substrate around by picking it up in their mouths and then spitting it out in a different spot.

It’s important to choose a substrate that is smooth and free of sharp edges to prevent cuts to the sensitive skin of the fish. Gravel is the most common type of substrate used for Oscars, with options ranging from large to small pieces.

In addition to providing a natural environment for the fish, the substrate can also contribute to the aesthetic appeal of the tank.

Tank Décor

Oscar fish prefer a tank environment that mimics their natural habitat. Here’s what they like in their tank:

  • Driftwood: They like driftwood in their tank. Driftwood can provide a natural and comforting environment for them.
  • Rocks and Rock Formations: They like rocks and rock formations in their tank. They often move around large rocks which are suitable for these large fish.
  • Caves: They like caves in their tank. Oscars will enjoy using caves as hiding spots.

In addition to these elements, Oscar fish also appreciate a variety of toys and decorations in their tank, including floating logs, ping pong balls, moss balls, waterwheels, floating tubes, and aquarium plants. However, it’s important to ensure that all toys and decorations have no sharp edges for the safety of the Oscar fish.

While tank decorations and hiding places are important, remember that they need open space in their tank as well. They are active swimmers and require plenty of swimming space.

Aquarium Plants

Keeping aquarium plants in an Oscar tank can have several benefits, but it also presents some challenges due to the nature of Oscar fish. Here are some points to consider:

Benefits of Aquarium Plants:

  • Emulate the Natural Habitat: Most fish’s natural habitat contains live plants. So keeping some live plants in the aquarium helps stimulate their natural habitat.
  • Oxygen: Plants increase oxygen in the aquarium through photosynthesis, which is beneficial for fish.
  • Food For Fish: Some plants can be a food source for the fish. It can also house aquatic insects and other small invertebrates, which will also feed the fish.
  • Natural Filters: Aquarium plants act as natural filters in your tank, helping to remove toxins from the water such as nitrates and phosphates which can be harmful to fish if left unchecked.
  • Shade and Privacy: In a well-planted aquarium, fish can find shade from glaring light, privacy from things outside of the tank that startle them, and a natural safety in times of stress.

Challenges with Planted Oscar Tanks: Oscars are large fish that can grow well over 12 inches long. They are very particular about their living spaces, and their finicky preferences can change over time. Oscars have a tendency to root through the substrate in their aquarium which can cause damage to the plant roots. Many aquarium plants are unable to tolerate this kind of treatment and they are likely to die if their roots are damaged. If you do plan to keep live plants in your Oscar tank, you need to be intentional about where you place them. Some hardy aquarium plants that may survive in an Oscar tank include Banana Plant, Java Fern, Java Moss, and Salvinia Natans.

With that said, some Oscars will not bother if you keep plants in their tank and others will destroy plants no matter what plant you keep in the tank.

Tank Mates

Oscar fish are known for their aggressive behavior, so choosing the right tank mates for them is crucial. Here are some fish that can be good tank mates for Oscar fish:

  • Convict Cichlid: They are very beautiful and are also called zebra cichlid due to the patterns of colors that extend over their bodies.
  • Jewel Cichlid: The jewel cichlid originates from Africa – the muddy rivers in central Africa.
  • Green Terror Cichlid: They are known for their bright green color and can be a good match for Oscar fish.
  • Jack Dempsey: Named after the famous boxer, they are known for their aggressive nature which can match with that of Oscar fish.
  • Jaguar Cichlid: They are large, aggressive and require similar water conditions as Oscar fish.
  • Firemouth Cichlid: They are relatively peaceful and can get along with Oscar fish if given enough space.
  • Blood Parrot Fish: They are hybrid fish that are generally peaceful and can live with Oscar fish.
  • Cichlasoma: They are a genus of large cichlids that can be a good tank mate for Oscar fish.
  • Bala Shark: Despite their name, they are actually a type of minnow. Bala Sharks are known for their peaceful nature.
  • Red Tail Shark: They are small, active fish and their vibrant red tail can add color to your tank.
  • Common Pleco: Common Plecos are large and have a tough, armored exterior, which makes them less susceptible to potential Oscar fish aggression. They are also efficient tank cleaners.
  • Sailfin Pleco: Sailfin Plecos are bottom dwellers and spend a significant time grazing on algae and other detritus. In contrast, Oscar fish are more mid-to-top dwellers, ensuring they occupy different tank strata and avoid territorial disputes.

Remember, Oscar fish can be hostile and highly territorial, so make sure you keep them in a large tank so that both fishes get adequate space to thrive. It is generally not recommended to add small fish, shrimps, and other small invertebrates in an Oscar tank since they will most likely not survive.

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