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What Size Tank For Oscar Fish: A Quick Guide For Beginners

what size tank for Oscar fish
Oscar fish, also known as velvet cichlids, are incredibly captivating with their unique appearance and fascinating behavior.

If you are planning to get an Oscar fish one question that may arise is: What size tank is best suited for Oscar fish?

Having the right tank size is crucial for Oscar to thrive and grow comfortably.

In this article, we’ll tell you about the ideal tank size for Oscar fish and provide other valuable information.

So without further ado, let’s get into it.

What Size Tank Do You Need For an Oscar Fish?

The recommended tank size you need for Oscar fish is 75 gallons. This is the ideal tank size for Oscar fish, since it provides them with the necessary space to grow, swim, and live comfortably.

Although several websites state that a minimum 55-gallon tank is sufficient, it is important to take into account the long-term needs and well-being of the fish. Therefore, opting for a 75-gallon tank is considered the best choice.

Oscars can grow up to 12 to 15 inches and can weigh over 3 lbs. With such impressive growth potential, it’s best to provide a larger tank that allows them ample space to thrive and swim freely.

Why Choose 75 gallons instead of 55?

“Why should I go for a 75-gallon tank instead of the minimum 55-gallon option,” You ask. Well, let me shed some light on that.

First, imagine an Oscar fish living its entire life in the tank. You wouldn’t want the tank to be too small and limit their ability to swim freely, would you?

With that said, let’s look at several other compelling reasons to opt for a larger tank:

Provides Sufficient Space

Oscar Fish requires a spacious tank due to their large size, as they can grow up to 1.5 feet in size at a growth rate of approximately 1 inch per month. Can you imagine the rapid growth the fish undergoes?

In a smaller tank like a 55-gallon or less, Oscar fish can quickly become cramped. By choosing a 75-gallon tank or larger, you provide sufficient swimming distance, allowing them to stretch out their fins and move comfortably, ultimately promoting their physical health and overall well-being.

Prevents Stress and Aggression

Oscars are territorial fish and can be aggressive toward tankmates if they feel cramped or stressed. A larger tank provides more room for other compatible fish to establish their territories and reduces the likelihood of aggressive behavior or conflicts.

Manage Bio-load

Oscar Fish eat a lot and are known for their significant waste production, which can pose challenges in smaller tanks.

Opting for a larger tank, such as a 75-gallon or even a 125-gallon tank (for 2 fully grown adult Oscars), provides a greater water volume to dilute the waste produced by the fish, reducing the impact on water parameters such as ammonia, nitrite, and nitrate levels. It provides a healthier and more stable environment for the fish.

This eventually helps to maintain better water quality for a more extended period and reduces the frequency of water changes, providing a healthier habitat for your Oscars.

Tank Setup Tips for Oscar Fish

When it comes to setting up the perfect environment for your Oscar fish, there are several key factors to consider. Let’s explore these tips to ensure your Oscars thrive in their new home:

Water Quality Maintenance

As we discussed, Oscar fish are notorious for their messy eating habits and waste production. Therefore, maintaining good water quality is of utmost importance.

Regular water changes and proper filtration are essential to keep the tank environment pristine and healthy for your Oscars.

Monitor water parameters such as temperature, pH levels, and ammonia levels. Ensure that the water meets the below criteria:

  •  ​Water temperature: 75-80°F
  •  ​pH levels: Between 6 and 7.5
  • Water hardness: 12-15dH

Proper Cleaning and Decoration

When setting up the aquarium, ensure all equipment and ornaments are properly washed to remove any chemicals or contaminants. To mimic their natural habitat, provide decorations and hiding places in the tank, such as live plants, driftwood, and gravel.

Good Filtration System

Oscars produce a significant amount of waste, so a good tank filter is essential for maintaining water quality. A canister filter is recommended due to its efficiency and ability to handle the waste produced by Oscars. Make sure to choose a filter that is rated for a larger tank capacity to handle the waste load adequately.

How Many Oscar Fish Should Be Kept Together?

what size tank for Oscar fish
Oscar fish are active fish and prefer to stay in pairs or in groups. Therefore, it is recommended to keep at least two Oscar fish together.

For two fully grown Oscar fish, you should get at least 125 gallons of tank space. And, for four Oscar fish together, you should get a tank that is larger than 200 gallons.

While keeping Oscar fish, it is best to keep a male and female in pair, but this is not mandatory.


In conclusion, Oscar fish require a spacious tank to thrive and exhibit their natural behaviors. While the minimum tank size is often cited as 55 gallons, opting for a larger tank, such as a 75-gallon, is highly recommended.

The additional space accommodates their growth and prevents stress, aggression, and territorial behavior. Furthermore, proper tank setup, water quality maintenance, and the inclusion of hiding places and decorations contribute to the overall well-being of your Oscar fish.

So, when it comes to housing Oscar fish, remember, bigger is better! With a suitably sized tank and a well-prepared environment, your Oscars will have the space to thrive and mesmerize you with their captivating presence.