Oscar fish in aquarium

Oscar Fish Care: Types, Tank Setup, Diet, And More

Known for their intelligence, aggression, playful behavior, and beautiful patterns, Oscar fish are one of the most popular species of freshwater fish. They’re smart fish and can even recognize their owners, especially around feeding time. 

In this guide, you’ll learn everything you need to provide quality care for this intriguing species of tropical fish. Let’s dive in!

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Oscar Fish Overview

Oscars, also known as Astronotus ocellatus, are a species of cichlid. Oscars originate from the South American family of cichlids.  They’re native to Brazil, Columbia, Ecuador, French Guiana, and Peru. Their primary habitat in the wild is the  Amazon river but wild populations have also been found in interesting places like North America and China, although this spread is only through the fishkeeping hobby. In other words, someone let their pet Oscar into a local body of water and it survived and reproduced.

Oscar fish are very popular for home aquariums, but that doesn’t necessarily make them beginner fish. They’re aggressive and territorial, like most cichlids, and like their name, can be a little grouchy sometimes.

That being said, Oscars are personality kings and queens. There are also a few different varieties if you’re interested in unique color patterns. They can also be the grandparents of the fish world, with reports of some Oscars living up to 20 years!

Because they’re so popular, you are likely to find Oscars for sale in most aquarium stores. They’re not as cheap as a neon tetra, but they’re also not as expensive as an arowana. Expect to pay about $5-10 for a fish, depending on their age and color patterns.


Oscar Appearance

Oscars are typically large fish, reaching up to 12 inches in length. They’re fast growers, with most growing about an inch per month until they’re fully grown. If you do the math, this means you could have a full-grown oscar in about a year! 

Their body shape is a long oval in a classical cichlid shape. Their bodies are covered in an assortment of irregular black and orange patches. Their colors can deepen or fade over time.

Given that they’re such a popular species, many varieties have been created through selective breeding, such as albino oscars and red oscars.


Types of Oscar Fish

Tiger Oscar

This is your common Oscar. Tiger oscars have red and orange patterns on top of a dark brown/grey base. They’re the original version of the breed so they possess the true characteristics and behaviors of typical oscar fish.

Red Oscar or Lemon Oscar

Red and lemon oscars span the range of red shades, from crimson and copper to rusty orange to pure lemon. These oscars don’t have the characteristic patch patterns of tiger oscars; they’re more of a solid color. Second to tiger oscars, they’re the second most popular oscar type.

Albino oscars

Albino oscars are white in color with red eyes. They often have red splotchy patches that somewhat resemble tiger oscars. However, their base coloring is white so they look quite different. Albino oscar behavior is similar to that of tiger and red oscars.


How long do Oscars live?

Oscars typically live 10-13 years, with some reports of fish living up to 20 years. Because their lifespan is often 2-4x that of other freshwater aquarium fish, be prepared for long-term care when you purchase this species.


How big do Oscar fish get?

On average, Oscars grow to about 12 inches in length, with reports of some fish reaching lengths up to 18 inches. They’re quick growers and will pack on an inch per month. So in other words, that cute little oscar in the fish store today will be a footlong adult in about a year. This is important when considering their tank size requirements.

three oscar fish in aquarium

Oscar Temperament

Oscar fish are known to be mildly aggressive and territorial fish. Their aggressive tendencies are known to increase during spawning. Additionally, they need a lot of space so if you put them in a tank that feels too small for them, you’re going to see even more territorial behavior and fighting. Oscars are also known to fight among themselves with bigger fish picking on smaller fish.

Despite all of these warnings, Oscars will generally do fairly well with other South American cichlids as tankmates, provided that their tank mates aren’t too aggressive or too passive. You need fish that will stick up for themselves but 

Won’t necessarily go picking a fight because they’re bored. 

Avoid smaller tank mates. Oscar fish are known for eating anything small enough to fit into their mouth. Guppies and smaller fish, like Chili Rasboras or Ember Tetras are top of the favorite snacks list.

Outside of their aggressive and territorial tendencies, Oscars are curious, active, and entertaining fish. They’re known for their intelligence and ability to recognize their owner, often swimming excitedly to the front of the tank when their owner shows up.


Oscar Fish Care

You want your oscar to live a long and healthy life so it is important to understand the key care parameters for them around tanks, substrate, filtration, lighting, and decorations. 

Let’s explore each element in more detail.


Oscar Fish Habitat

When planning the ideal Oscar tank, it is recommended to try to recreate their natural environment. This principle works well when designing tanks and making sure your fish are eating correctly. Recreate the natural environment for best results. 

Oscars are South American cichlids, originating in the Amazon river areas. That means they’re used to environments with tree branches and roots, rocks, and flowing water. Their water is also not perfectly pristine and clear. 


What is the best tank for an Oscar?

Oscars can grow to be quite large. They’re also territorial, which means they need more space (if there are multiple fish in a tank) to not feel like their space is being cramped. This means you need a large tank. The minimum recommended size tank for a single Oscar is 55-gallons. That’s the absolute minimum. The ideal tank size for a single Oscar would be closer to 75 gallons. 

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What if you want to add more than one Oscar to your tank? Well, simply put, you’re going to need a much larger tank! Here are our recommendations for tank sizes when you have more than 1 Oscar:

  • 1 Oscar – 55 gallons
  • 2 Oscars – 125 gallons
  • 3 Oscars – 150-200 gallons

These tank sizes might scare you but remember, larger bodies of water are typically easier to maintain consistent parameters. There is more water to dilute any bad water parameter situations so it is much less likely for your tank to experience rapid fluctuations.

How many Oscars can go in my tank?

Oscars can be kept together in a species only tank. This is usually one of the safest options in terms of tank mate compatibility. Oscar Fish do seem to enjoy living in pairs or small groups. We would recommend keeping at least 2, or even 5 if you have space. However, we would avoid a group of three, as two of the fish could bond, leaving the third one feeling left out and stressed.

Make sure their tank is large enough or else you will run into quarreling Oscars in territory disputes. 


Ideal Oscar Water Conditions

Oscars are highly sensitive to water changes so it is crucial that your water parameters are suited to the needs of your oscar fish. This sensitivity is another reason why categorize the Oscar as an intermediate to advanced fish. Making a mistake with your water parameters could result in a dead Oscar, which is really sad, especially when you consider their potential lifespans.

Oscar fish thrive in the warm waters of the Amazon River Basin. These are the water conditions we are trying to create:

  • Temperature: 74 and 81 degrees Fahrenheit (ideal 77 degrees Fahrenheit)
  • pH level: 6-8 (ideal 7.2)
  • Water Hardness: 5-20 KH

The key with all of these parameters is stability. For example, it is better to have a slightly less ideal temperature – say 75 degrees – than to continually chase 77 degrees, overshoot it, heat the water to 82, try to cool it back down again, bring it all the way to 73, and start over again. Constant change puts stress on your fish so shoot for stability first in your parameters.

In order to maintain stable water conditions, we recommend testing your water with this Aquarium testing kit

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Because of their sensitivity to water conditions, do not add Oscars to uncycled or newly cycled tanks. They are not good candidates for cycling. They are big fish and produce a lot of waste, so they will cause dramatic water parameter changes in new tanks. Better to just avoid losing your beautiful fish. The nitrogen cycle needs to run its course and stabilize before adding any Oscars.


How Much Water Flow do Oscars Need?

Oscars naturally thrive in flowing river water. This means they also like a moderate to high level of water flow in the tank. We recommend a water turnover of 4 times per hour.

As long as your fish swim comfortably, high-flow conditions are the preferred state. If you make your tank high flow and you notice your fish are struggling to swim comfortably, you can either turn down the flow slightly or you can add a few rocks or decorations to the tank to break up the flow.


What to put in your Oscar tank

Ok, now that we have the basics of tank, water parameters, and water flow in place, we come to the question – What should I put in my Oscar tank?

What is the Best Type of Substrate for Oscars?

Both sand and gravel work well as substrates for Oscar tanks. When evaluating the two options, it is important to consider typical Oscar behavior. Oscars, like most cichlids, enjoy digging and rooting around in their tanks. They will often take in and spit out substrates, like sand. Over time, if your Oscar happens to spit out sand directly into your filter uptake, it can break the filter, costing you an unexpected sum of money.

To avoid this situation, you can add a pre-filter into your tank to prevent this situation if end up going the sand as a substrate route. 

If you go the gravel route, make sure your gravel has soft rounded corners so your Oscar doesn’t tear up his mouth playing around with the rocks. 

How Much and What Kind of Lighting do Oscars need?

Oscars are pretty lowkey about lighting. This means they don’t need any special lighting set-up. A basic room lit by daylight will work for them.

However, if you do want to purchase lighting, keep in mind that oscars prefer moderate-low lighting. Think about their natural habitat in the Amazon river basin – it is water that is full of natural plant matter that falls into the river from the canopies above. This means light conditions are moderate at most.

This means you should not leave your bulb on for more than 12 hours at a time. If you leave it on longer, you will likely stress for fish. 

Keep on eye on your Oscars’ behavior when you turn on the lights. If you have an oscar that shies away when your bulb is on, then you may want to consider dimming, getting a lesser strength bulb, or removing your light.

If you’re curious about the best LED lights for aquariums, check out our guide.

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What Kind of Filtration do Oscars Need?

Oscars are big fish that are pretty messy (large bioload / waste output), which means you will need to stay on top of their water purity. Additionally, they are very sensitive to water changes and ammonia levels. This means you’re going to need a high-quality filtration system to keep your tank in perfect condition. 

For these reasons, we recommend a HOB or canister filter option. Sponge filters aren’t going to cut it in this situation. Your filtration system should be strong enough to turn over the entire volume of your water four times per hour.

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Decorations

When feeling threatened, Oscars like to hide in order to feel safe. When your Oscar is young, small, and vulnerable, this tendency is especially pronounced. This means they will appreciate any nooks and crannies you create via decorations. 

However, Oscars are known for their tendency to rearrange their territories; they will take joy in moving small items around their tanks. Because of this reason, it is advised to avoid any breakable decorations, like ceramic objects.

Oscars are also clumsy; they will constantly knock into things. To help keep them safe, avoid objects with sharp points or rough textures, because your Oscar will likely injure themselves on it. 

Lastly, avoid adding decorations like coral, limestone, and other calcium-carbonate based minerals. These items will leach into the water over time, changing the pH. Oscars are sensitive to pH changes so this could make their tank less habitable over time. 

Plants

Oscars are cichlids. Cichlids are notorious plant destroyers and uprooters. If you have real plants inside the tank, be prepared for them to torn up if you’re lucky, and destroyed if you’re less lucky. We don’t normally recommend fake plants, but with Oscars, fake plants are where its at.  

If you absolutely must go the live plant route, pick something hardy. We recommend plants like the Java Fern or Amazon Swords which are a little bit tougher and more durable.


Oscar Fish Potential diseases

Important notice: we are not veterinarians at Aquarium Friend so the information below should be used for general awareness only. If you are concerned about the health of your fish, consult a fish health professional immediately.

Oscar fish are hardy fish but that doesn’t mean they aren’t pronte to catching number of illnesses.

An Oscar-specific disease is hole in the head disease. If you’re thinking it sounds scary, you’re right, cause it is scary. 

The disease follows its name closely.  It is easy to spot the disease because you can literally see pitting holes forming in your fish’s head and body. It is more common in older Oscars than younger Oscars.

The exact cause of hole in the head fish disease is not yet known but there are several theories around that link certain conditions with an increase in the incidence of the disease. By keeping an eye out for these conditions, you can reduce the likelihood of your fish getting ill.

First, the flagellate parasite Hexamita is commonly linked. This parasite primarily infects the intestinal tract, but then spreads to other internal organs. As it spreads, the head holes begin to appear. From there, bacterial or fungal infections may develop in these openings, leading to more serious disease.

Another theory is that a mineral or a vitamin imbalance may contribute. Some aquarists have claimed the use of activated carbon increases the risk of this disease. Their theory is that the carbon removes beneficial minerals found in the water, throwing off of the overall balance for healthy fish. 

Like most fish illnesses, high-stress conditions, such as poor water quality, improper nutrition, and overcrowding, will also increase the incidence of this disease. 

Head in the hole disease is fatal if not quickly addressed.


Oscar Fish Feeding 

In the wild, oscars are omnivores, with their diets consisting of things like insects, smaller fish, worms, plants, and fruit from the canopies above.

Oscar fish with beautiful orange color

What should you feed an Oscar?

Like most elements of keeping freshwater fish, you should aim to replicate their natural diet as closely as possible.

Oscars do best with a high-quality, high-protein diet with a variety of processed, frozen, and freeze-dried foods.

For starters, get a high-protein commercial fish food produced for carnivorous species (such as cichlid pellets). Your cichlid pellet food should comprise the majority (80%) of your oscar’s diet.

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For the remaining 20% of their diet, plan to supplement with live, natural food. This may include:

  • Crickets
  • Locusts
  • Grasshoppers
  • Mealworms

Avoid poultry and beef heart with Oscars because you want to keep them lean. 

How Often Should I Feed my Oscar?

Oscars are fast growers, about an inch a month, which means your baby oscars are going to act like they’re hungry all the time.

However, you should stick to a strict schedule, as overfeeding is bad for both fish health and tank health, as it could dirty your water conditions very quickly.

We recommend starting with 3-4 pellets, and let your Oscar fully consume them. Keep adding pellets 3 or 4 at a time, for up to three minutes. Stop at any point if your fish fails to quickly consume them. 

We recommend feeding two times a day to avoid issues with overfeeding.

Once your oscar is about halfway grown (5-6 inches), you can start supplementing with mealworms and grasshoppers during feeding times.


Oscar Tank Mates

Oscar Fish are not the friendliest fish on the block, even in their native environment of the Amazon river basin. So you can imagine that when you start to limit space, going from the Amazon river to a 200-gallon tank, Oscars can feel cramped and territorial. Oscars do best with other Oscars if you have the space for multiple fish.

However, if you do want to keep other fish with your Oscars, make sure they are on the larger side. A few Oscar fish tank mates that could work include:

  • Large Plecos
  • Arowanas
  • Convict Cichlids 
  • Jack Dempseys

Any small fish will be promptly consumed as a snack. The same goes for invertebrates such as shrimps and snails. Don’t mix them if you want to keep both species alive longterm.


Breeding Oscar Fish

Breeding Oscars is possible, but it is not necessarily easy. They have extremely high standards when choosing mates, so your Oscars might not have eyes for one another. Forming an Oscar pair is not as simple as throwing two fish together in a tank so be patient when trying to bond a breeding pair.

Oscars must be sexually mature in order to reproduce; maturity occurs around 16 months – 2 years of age. You can not breed with juvenile oscar fish.

Breeding Oscars can produce some beautiful color outcomes, as you can breed any combination of oscar fish – tiger, red or albino – together.

How to Sex Oscars

Sexing oscar fish can be difficult. They are monomorphic, meaning that both sexes are virtually identical in appearance. The sex can only be determined when they are at least one year old. There are no distinguishing features before then.

In order to sex Oscars, you must look at their genitals. The female oscar has an egg tube that retracts fully inside of them, while males have a single sharp spike used for fertilization. If you’re not an expert, this is going to be very difficult to identify casually.

The Breeding Process

When Oscars are about to breed, the female will swim around with her belly almost touching the surface where she will lay her eggs. Oscars often choose a flat rock. She will often clean the surface of the rock with her mouth in preparation for the breeding ritual.

During this time, the male Oscar will be closely watching and following behind the female. As the female lays the eggs, he will spread his milt over the eggs. 

Oscar fry will hatch within 72 hours. On occasion, Oscars will eat their eggs. If you want to maximize the chances of your Oscar fry hatching, consider moving the parent fish into another tank while the Oscar fry grows.


 Oscar Fish FAQs

Are Oscars aggressive?

Oscars are a species of cichlid, so they are territorial and aggressive. However, on the scale of cichlids, they are relatively docile, especially compared to species such as the Wolf Cichlid and the Jewel Cichlid. Oscars originate from the Amazon River basin, where they share their waters with a multitude of other fish species. This means that in a large enough tank, an Oscar can be housed with other fish. Oscars get along with fish who are similar in size and are not too passive nor too aggressive. You need tank mates that can stick up for themselves but aren’t necessarily going to pick a fight.Every Oscar has its own level of aggression, with some more feisty than other.

Do Oscars have teeth?

Oscars have teeth – two sets actually. However their teeth are not very sharp. Though an Oscar might bite you during tank cleaning and you might bleed a bit, you’re not at risk for serious injury. 

How fast do Oscars grow?

Oscars grow about one inch a month, until they reach full size of about 12 inches.

Do Oscar fish recognize their owners?

Oscar fish are also known as water dogs or river dogs because of their ability to recognize their owners and get excited. Oscars are considered smart fish because they recognize and will interact with their owners. They can recognize their keepers by sight and sound (through vibrations from footfalls) and are more likely to show excitement when the family members who typically feed them approach the tank.

Do Oscar fish like mirrors?

Oscar fish will likely take the reflection as a “new” oscar in their tank and might get a little bit feistier because of it. Some Oscars deepen their color when they see a fish in the mirror, because of the perceived threat so its not advised to permanently attach the mirror to the tank, as it will stress your fish over time.

Why do Oscar Fish Jump Out of the Tank?

There are a few situations that could cause your Oscar fish to jump out of the tank. First, if they see something above the tank they want to eat, they will likely jump to try to grab it. Oscar fish are also know to jump out tanks with bad water quality, especially if the ammonia levels get too high. Lastly, if your Oscar is being bullied by other large aggressive fish, it might make a jump for safety.


Conclusion

Now that you’ve learned just about all there is to know when it comes to caring for Oscar fish, you should be able to decide for yourself if they’re a good fit for your aquarium.

Oscar fish are beautiful, energetic, and intelligent freshwater fish. Also know as water dogs, they are known to recognize their owners. However, they can be aggressive, so you have to mindful about sufficient tank size and tank mates before adding additional fish.

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