Setup a tank for Oscar Fish: Step By Step Guide

Oscar Fish is the species that inhabit the freshwater. You can mainly find Oscar Fish in the subtropical region. Oscar Fish is known for its familiar behavior; it is said that the fish recognize its owner. Oscar Fish is comparatively large than other fish and has the habit of defending their territory, so they get into fights with other fish and require space of their own. So before getting an Oscar Fish, you have to have a decent knowledge of how to setup a tank for oscar fish correctly. For your oscar fish to live a healthy and enjoyable life, the environment should be equal to its natural state.

Inside an aquarium, an Oscar can grow up to 10 inches long and live an average life of 10 years. If proper care is given to the fish its life expectancy can increase a couple of years. The tank setup is essential before bringing your oscar fish. You must consider things like tank size, water condition, which filter to use, how many fish to keep, and environment and ornaments set up before bringing an oscar fish into your house.

Choosing Correct Fish Tank and Accessories for Oscar Fish

You require proper accessories and types of equipment for the healthy oscar fish. Accessories include ornaments, gravel, filter, food, lighting, and other environment supporting things.


Picking Your Oscar Tank

People think they can keep oscar in a 25-gallon aquarium but forget that an adult oscar fish can get to 10-12 inches long. I advise you to use a 100-gallon aquarium. If you keep more fish inside a confined space, it will add maintenance works like changing the water frequently and cleaning the water tank more often. Not only this but also a threat to injuries to your oscar. Experts regard Oscar fish as fish with a high appetite; the more the food, the more the waste and cleaning requirements, keeping oscar in narrow space increases the chance of poor water condition, contamination, and disease. Thus, we need to put on the proper filter system to maintain the quality of water.

Do Oscar Fish Need a Filter?

 Having a filter system in an aquarium is as important as having a liver or kidney inside a human body. The filter clears all the unwanted stuff out of the aquarium, maintaining the quality of the water cleaner and habitable for the fish. The water regulation interval of the filter should be fast to clear all the toxins out of the water to make the fish sick. I personally use a slightly higher accessing level water filter than the size of the aquarium and recommend you to do the same. For example, you have an aquarium of 75-gallon. I recommend you to use a filter designed for 100-gallon. Talking about the big-size tank, I use a 36 inch by 15 inches by 18-inch custom made sump.

Do Oscar Fish Need a Heater?

Oscar fish are originally from the sub-tropical region; this means they are used to the heated environment. Proper water temperature is very important for the oscar fish to have a healthy life. Oscar can live in the temperature as low as 21 degrees and can survive up to 30 degrees. The best temperature for oscar fish throughout the year is 27 degrees. Oscars have a high degree of destructive nature; they are frequently reported to break things inside the aquarium. Hence you must equip your aquarium with the strong hard glass titanium made heater to safeguard the heating system.

If you use regular heaters, Oscars will destroy those things in pieces. We have to find the perfect heater for the size of the aquarium, a heater of 500wt is perfect for the aquarium of 125-gallon water. But I would recommend you to use two heaters of 300 Watt. This way if one fails, the next one will do its job.

Adding substrate/gravel and plants

The substrate is essential for your aquarium. The inclusion of sand and gravel in the mix of the aquarium can help maintain the natural environment of the fish. To make your aquarium look fancy, the pet store is available with a different color of sand. Another great inclusion in the aquarium would be driftwoods. Large pieces of wood provide playgrounds and shelter for fish, keeping the presence of real-life environments inside the aquarium. You may wonder that woods do float in the water, don’t worry at first it seems to float but will saturate and sink eventually. Despite that, you can always attach additional weight to the driftwood.

Another thing that can be added inside the aquarium is the plants. Oscar fish tends to destroy the plants for fun, as of its destructive nature. Oscars feel the toughness by destroying the plants and substances inside the aquarium, so I suggest you use artificial plants. There is a big chance that the Oscar will still uproot the plant, but in the case of artificial, we can again install it where it belongs.

Lighting For Oscar

As being the inhabitant of the tropical region, Oscar fish doesn’t require specialized lighting. Though in order to decorate your aquarium and see your fish clearly, you can always use sightings of mainly white and blue, preferable marine blue and smoke white lights. But if you have any plants included in your aquarium, you will have to maintain lighting for the plants. Oscars seem to enjoy the dim and murky environment if you could generate that lighting the oscar will be happy.

Step By Step Guide to Setup a Tank for Oscar Fish

Accessories and tank setup for Oscar are slightly different than other fishes. Oscar has a destructive nature and is quite large, and they require a high degree of attention. That requires a tank setup for the Oscar in a different manner.

Step One: Preparing and Placing the Aquarium

Preparing the tank location is the first and foremost task to be done before purchasing the tank. The tank location will be idle in the living room. Oscar is not the silent type of fish. They are active and full of life and are a delight to watch. Preparing the aquarium needs the proper water filtration, use of equipment and gravel, lighting, and quality water tank. Oscar fish are evolved to live in the subtropical region, so we should be able to create a subtropical environment in the tank.

Step Two: Installation fo filter and heating system

After the tank is set up and properly placed, the next big task is to install the filter and heating system. The filter should be able to clear the waste material from the water. Oscars are the being of freshwater, so they are not resistant to toxins and acid Therefore, your aquarium water should be properly filtered or else your fish is going to get diseases.

Read our article on Oscar Fish Diseases and treatments.

Step Three: Adding gravel and ornaments

Using gravel and ornaments is the next step of the aquarium setup. I recommend you not to use expensive gravel as Oscar fish is the inhabitants of the real freshwater and are evolved to live in the same environment. Mostly expert recommends to use standard gravel, but in case of oscar, you can use the cheapest gravel available. If you want to decorate your aquarium in the prettiest way and to delight the eyes, you can use colorful stones, which will be a show to watch. You can also use other ornaments in the aquarium to provide enough playgrounds in the aquarium for your oscar fish. If you wish you could introduce some plants in your aquarium, you can bring in some artificial plants because Oscar is destructive in nature to the plants. They tend to destroy the natural plants in the short time of the introduction. Hence if you bring real plants, it will cost you more money.

Before you add your decorations, rocks or gravel, make sure you clean it with clean water to remove any chemicals from them. OR else, your tank water might get contaminated with the toxins that came out with the decorations from the factory.

Step Four: Adding water to the tank

Filling water in the tank is to be carried out very carefully as possible. Before filling up the tank with the water, check your water parameter and treat your water. Also, the condition of the filter and other equipment are to be fully tested. After that, with all being ok, the freshwater is to be added and left in for a while.

Step Five: Turn on filter and heaters

Once the water level matches the optimum level of the aquarium, the next step is to Turn your aquarium filter on and start the heating system.  Filtration recycles the water and filters it again to reduce the toxin level of the water. A filter helps in the aquarium nitrogen cycle process where beneficial bacteria that colonize in the filter media will feed on Ammonia and nitrite converting it into less harmful form nitrate. Oscar fish is the natural habitat of the subtropical region as it requires mild temperature, so a proper heating system should be introduced in the aquarium.

Step Six: Perform a Fishless Cycle

Once a tank is properly set up, the next step is to perform a fishless cycle. this might take from a week to a month. in this duration, you need to monitor your tank water condition by testing pH, hardness, ammonia, nitrite, and nitrate level. If the fish is introduced without a complete cycle, then fish can catch the contamination and bacteria.

You can use a filter media from a well-established tank to boost up the nitrogen cycle in your new aquarium.

Step Seven: Introducing the fish to the tank

Once you complete the fishless cycle, you can add fish to the tank. But keep in mind; you shouldn’t introduce all your fish at once into the tank. Test for one fish at a time for one day. And after the succession, introduce other fish into the aquarium. You must use water test kits to test the quality of water, and should also check the filtration very carefully when you introduce the fish to the tank. If you notice any abnormal behavior, then you should supervise the tank again.

How to Choose a Healthy Oscar Fish

To spot a healthy Oscar fish, the basic thing is to look at the swimming patterns and livelihood of the fish. Oscar fish are the subtropical fish, and they are full of life, they tend to play around humans. Another way to check the fish condition is by feeding the fish. If the oscar fish accepts the food, they are healthy, if they don’t, they are not healthy.

Things to remember

  • Oscars are famous for aggression, so space should be adequate for the Oscar fish. Filtration and heating are the major importance of aquarium fish.
  • You must maintain the water level according to the aquarium size (water should always 1-1.5 inches below the surface of the tank).
  • You should change about 15-25% of the tank water every week.
  • Next, you need to feed your oscar fish a healthy diet regularly.
  • You must check the filter and heater of your aquarium regularly.


At last, I will conclude the article on “How to setup Tank for oscar fish” by reminding you of major points that you should not forget while setting up Oscar Fish tanks. Those points are :

  • The purchase decision of the fish.
  • Selection of the tank and location.
  • Decorating the tank with ornaments and accessories.
  • Filter and heating.
  • Fish introduction
  • Water change in the tank

If you follow these steps correctly and sequence, the tank setup will be perfect. We should not rush ourselves in the purchase and bringing the Oscar. We should patiently wait and buy with major caution and proper decision. Oscar fish require great attention. The owner should be completely ready for the Oscar fish to be introduced in their life.

If you are looking forward to reading more interesting articles on Oscar or other fish, then I recommend you to visit my website Fish Keeping Guide.