Oscar Fish Tank Size (A Complete Guide)

This is a complete guide to Oscar Fish tank size.

Many people have confusions and there are a lot of conflicting opinions on the internet about tank size for Oscar Fish.

After reading this article, hopefully, all your doubts about Oscar Fish aquarium size will be declared.

So let’s get started.

Ideally, you should provide a 55 gallon tank for a single Oscar Fish, plus 20 to 30 gallons for every new Oscar Fish or the space required for any other species of fish.

Oscar Fish Tank Size (A Complete Guide) image

Oscar Fish minimum tank size

Oscar Fish can grow very large. It can grow up to 20 inches long.

Also, it grows very rapidly at a rate of 1 inch per month.

Ultimately a full-grown Oscar Fish requires a large tank.

So ideally, you should keep Oscar Fish in a large tank of at least 55 gallons. The larger the better!

You can keep 4-5 juvenile Oscar Fish in a small tank of 30 gallons.

But as mentioned earlier, they can grow pretty fast and ultimately you will have to upgrade the tank and keep them in a larger tank to avoid stunting.

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How much space for more than one Oscar Fish?

two oscar fish

Image by Retro Lenses under CC BY 4.0

Oscar Fish can live up to 20 years and it can grow up to 12 inches.

For one Oscar Fish, you will require at least a 55-gallon tank and for every new addition of Oscar Fish you will require an extra 20 to 30 gallons.

So, for keeping 2 Oscar Fish in a tank you will require at least a 75-gallon tank.

In the same way, for keeping four Oscar Fish in the same tank you will require at least a 120-gallon tank.

Oscar fish can grow pretty large, up to 20 inches.

Also, they are very messy fish i.e. they produce a lot of waste.

Also, Oscar Fish belongs to the cichlids family which are known for their aggression.

And providing a larger tank will help to reduce aggression among Oscar Fish.

So when it comes to aquarium size for Oscar Fish, the more the better!

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Best Oscar Fish tank mates

Oscar Fish belongs to the cichlids family and they are known for their aggressive behavior.

Oscar Fish is no exception and they are quite aggressive fish.

That’s why you have to be very careful while choosing tank mates for Oscar Fish.

While choosing tank mates for Oscar Fish, you have to keep a couple of things in mind.

  1. The first thing is you should keep the fish that are are similar to the size of your Oscar Fish and that can hold their own against Oscar Fish.
  2. The second thing is you should avoid keeping the fish that are very small in size because Oscar Fish can easily eat them.

Basically, whichever fish that can fit into the mouth of your Oscar Fish you should avoid keeping it in the tank.

Usually, other fish that belong to cichlids family are good tank mates for Oscar Fish because they can get pretty large and can hold their own against Oscar Fish.

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Oscar fish tank mates

A few examples of good tank mates for Oscar fish are as follows:

1. Convict Cichlids

Convict Cichlids

Image by Deanpemberton under CC BY-SA 3.0

PARAMETERSVALUES
FISHConvict Cichlid
Common namesZebrafish
SCIENTIFIC NAMEAmatitlania nigrofasciata
FAMILYCichlidae
CARE LEVELModerate
MAXIMUM SIZE6 inches
AVERAGE LIFESPAN8+ Years
DIETOmnivore
WATER TEMPERATURE79 and 84°F
WATER pH6.6-7.8
WATER HARDNESS6 – 8 dGH
BREEDINGEgg layers
MINIMUM TANK CAPACITY30 Gallons

Convict cichlids are one of the best fish you can keep as a tank mates in your Oscar Fish tank.

Convict cichlids are also known as Zebra cichlids because of their appearance.

They have 8-9 black stripes throughout their body that look similar to zebra.

Convict cichlids are not very small so they will not get eaten by your Oscar Fish.

And as they belong to the Cichlids family, they can hold their own against Oscar Fish.

This fish is very territorial and it will form territory in your tank.

It spends most of it it’s time in the territory so it will not bother you Oscar Fish.

This fish can get pretty large up to 6 inches so it will not fit into the mouth of your Oscar Fish.

And this fish requires at least a 30-gallon tank.

Food

Convict cichlids are omnivorous so they will eat whatever you put into their tank.

Though they are omnivorous, their diet mostly consists of meaty food.

So you should mostly feed them cichlids flakes and pellets.

Occasionally treat them with frozen or live bloodworms, brine shrimp, etc.

And as they are omnivorous you should occasionally feed them vegetables.

Water parameters

The ideal temperature for convict cichlids is between 74 to 81° Fahrenheit.

Its pH tolerance range is between 6-8 and the hardness tolerance range is between 5 to 20 KH.

So the ideal water parameters that a Convict cichlid require are similar to that of Oscar Fish. So you can easily keep them in the same tank.

2. Firemouth Cichlid

Firemouth Cichlid
PARAMETERSVALUES
FISHFiremouth Cichlid
SCIENTIFIC NAMEThorichthys meeki
FAMILYCichlidae
CARE LEVELEasy
MAXIMUM SIZE7 inches
AVERAGE LIFESPAN15 years
DIETOmnivorous
WATER TEMPERATURE75-86°F
WATER pH6.5-8.0
WATER HARDNESS8-15 dGH
BREEDINGLive bearers
MINIMUM TANK CAPACITY30 gallons

Firemouth cichlids are colorful and popular cichlids in the aquarium hobby.

This fish is hardy and easy to care for which makes it an ideal choice for beginners.

It can get as large as 7 inches so it will not fit into the mouth of your Oscar Fish and will not get eaten.

The minimum tank size requirement for a single Firemouth cichlid is 30 gallons.

As Firemouth cichlid belongs to cichlids family, they can hold their own against Oscar Fish.

Food

Firemouth cichlids are not fussy eaters.

They are omnivorous and eat anything you put into their tank.

Primarily, you should feed them cichlids flakes and pellets.

You should also feed them meaty foods such as frozen or live bloodworms, brine shrimp, etc.

And occasionally you should also feed them vegetables such as spinach, boiled peas, etc.

Water conditions

The ideal water temperature for Firemouth cichlid is between 75 to 86° Fahrenheit.

Its pH tolerance range is between 6.5 to 8 and the hardness tolerance range is between 8 to 15 KH.

These water parameters are similar to the ideal range that an Oscar Fish prefers. So you can easily keep both the fish in the same tank.

3. Silver Dollars

Silver Dollar

Image by Haplochromis under CC BY 2.0

PARAMETERSVALUES
FISHSilver Dollar
FAMILYCharacidae
CARE LEVELIntermediate
MAXIMUM SIZE6 inches
AVERAGE LIFESPAN10 years
DIETOmnivores
WATER TEMPERATURE75-82°F
WATER pH5.5-7.5
WATER HARDNESS4-18 dGH
BREEDINGEgg layers
MINIMUM TANK CAPACITY75 gallons

Silver Dollars are good tank mates for Oscar Fish that don’t belong to cichlids family.

This fish got its name from its appearance.

It has literally flattened silver body that looks similar to an old silver dollar.

It is a schooling fish so you should keep them in at least a group of 4-5.

Silver Dollar is an active fish it can easily survive in an Oscar Fish tank.

This fish can grow up to 6 inches so it will not fit into the mouth of your Oscar Fish and will not get eaten.

As the Silver dollar is a schooling fish that can grow up to 6 inches, you should keep it in at least a 75-gallon tank.

Food

Silver dollar is an omnivorous fish.

Its diet is mostly a herbivorous diet.

So you should primarily feed it plant-based food such as vegetables like lettuce, cucumber, spring-greens, etc.

You should also feed them large vegetable flakes.

As they are omnivorous, you should occasionally feed them meaty food such as bloodworms, brine shrimp, etc.

You should feed them the food that they can consume within 3 minutes or less.

And you should feed them twice a day.

Water condition

The ideal water temperature range for Silver dollar is between 75-82° Fahrenheit.

Its pH tolerance range is between 5.5 to 7.5 and the hardness tolerance range is between 4-18 KH.

So the ideal water parameters range of Silver dollar is quite similar to that of Oscar Fish. 

So you can easily keep them in the same tank.

4. Bichirs

Bichir

Image by Stan Shebs under CC BY-SA 2.5

PARAMETERSVALUES
FISHBichirs
SCIENTIFIC NAMEBichir
FAMILYPolypteridae
CARE LEVELIntermediate
MAXIMUM SIZE30 inches
AVERAGE LIFESPAN15-20 Years
DIETCarnivore
WATER TEMPERATURE77-84° F
WATER pH5-7.5
WATER HARDNESS8 - 12 dGH
BREEDINGEgg layers
MINIMUM TANK CAPACITY90 Gallons

Bichirs are another good tank mate for your Oscar Fish.

This is a bottom dweller fish and spends most of its time near the substrate.

Oscar Fish spends most of its time in the middle part of the tank so it will not bother you Oscar Fish.

Bichirs are also nocturnal fish i.e. it will stay active during the night and during the day it will spend most of its time hiding behind decorations or near driftwood.

So they will not bother your Oscar Fish during the day.

Bichirs are moderately aggressive fish so they can hold their own against Oscar Fish.

This fish can get very large up to 30 inches so there is no way that it can fit into the mouth of your Oscar Fish.

But this is the reason you need a very large tank to keep them with your Oscar fish.

For a single Bichir fish, you will require at least a 90-gallon tank.

Food

Bichirs are carnivorous fish.

So there diet is consists of meaty food such as frozen or live bloodworms, brine shrimp, etc.

You can also feed eat meat such as Oxheart and earthworms.

You can also feed it sinking flakes and pellets.

Water conditions

The ideal water temperature range for Bichirs is between 72 to 82° Fahrenheit.

Its pH tolerance range is between 6.5 to 7.5 and it prefers softer water.

So its ideal water parameter range is quite similar to that of Oscar Fish. So you can easily keep them together in the same tank.

5. Placostomus

Sailfin Pleco

Image by Wisky under CC BY-SA 3.0

PARAMETERSVALUES
FISHSailfin Pleco
COMMON NAMESSailfin pleco, leopard pleco, gibby pleco
SCIENTIFIC NAMEPterygoplichthys gibbiceps
FAMILYLoricariidae
CARE LEVELEasy
MAXIMUM SIZE19 inches
AVERAGE LIFESPAN20 years
DIETOmnivorous
WATER TEMPERATURE77-79 °F
WATER pH6.5-7.4
WATER HARDNESSKH 6-10
BREEDINGEgg layers
MINIMUM TANK CAPACITY100 gallons

Pleco is another bottom-dwelling fish you can keep in your Oscar Fish tank.

As it is a bottom dweller fish, it will spend most of its time near the bottom of the tank and will not bother your Oscar Fish.

Besides, Plecos are nocturnal fish which means that they stay active during the night and feed during the night. And will hide near plants, driftwood or any ornaments in your tank during the day.

So basically, when your Oscar Fish is active Pleco is inactive and when your Oscar Fish is inactive during the night Pleco will be active.

So they will not bother each other and can live peacefully in the same tank.

Food

Plecos are omnivorous but they mostly feed on algae in your tank.

So they will also help to keep your tank clean.

Their diet mostly consists of algae and vegetables.

So you should feed them algae wafers and boiled vegetables such as zucchini, spinach, lettuce, etc.

But as they are omnivorous, you should also feed them meaty food such as bloodworms, brine shrimp, earthworms, etc.

Water conditions

The ideal temperature range for Pleco is between 74 to 80° Fahrenheit.

Its pH tolerance range is between 7-8 and the hardness tolerance range is between 3 to 10 KH.

So the ideal water conditions for Pleco are very similar to that of Oscar Fish so you can easily keep them both together.

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Oscar Fish Breeding Tank Size

baby oscar fish

Oscar Fish can get very big.

Usually, in captivity, Oscar Fish can get up to 12 inches and it can get up to 13 to 14 inches.

So ideally for a pair of Oscar Fish you will require a 120-gallon tank.

You should purchase already mated and spawned Oscar Fish to put into your breeding tank.

Or another way is to get at least 6 to 7 juvenile Oscar Fish put them in a tank and grow them together.

Then identify the pair and keep it in a separate tank.

The latter process is very time-consuming.

To successfully spawn Oscar fish, the fish should be at least 16 months old.

So if your only goal is to breed Oscar Fish then you should purchase already mated and spawned pair of Oscar Fish.

Besides, maintaining clean and clear water is very important for successfully breeding Oscar Fish.

To keep the water clean and clear you should use a large canister filter and a hang on the back filter for the breeding tank.

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Oscar Fish Tank Care

oscar fish

Now we are going to talk about how to take care of your Oscar Fish tank so that your Oscar Fish will have the ideal environment to thrive in your aquarium.

Temperature

Oscar fish prefers warmer water. The ideal temperature range for Oscar Fish is between 74 to 81° Fahrenheit.

So you should regularly check the water temperature of your tank with a thermometer and try to keep it under this ideal range. Check out our recommended Thermometer

If you notice high-temperature level in your Oscar Fish tank then you can try these ways to reduce the temperature in your tank.

If you notice the low temperature in your Oscar Fish tank then you can introduce a heater into the tank to raise the temperature. Checkout our heater recommendation.

You should also try to avoid water temperature fluctuations.

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pH and hardness

The ideal pH range for Oscar Fish is between 6-8 and the ideal hardness level is between 5 to 20 KH.

So you should regularly check the pH and hardness of the water with a testing kit and try to keep it under the ideal level.

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Nitrogen compounds

Elevated Nitrogen compounds such as Nitrate, Nitrite, and ammonia are very harmful to Oscar Fish.

Sudden spikes in the ammonia level can cause loss of color and hunger in your Oscar Fish.

Ideally, your tank should not contain any ammonia.

The Nitrite level should be zero.

And ideally, Nitrate level should be zero but Oscar Fish can tolerate nitrate up to 40 PPM but still, you should try to keep it as low as possible.

To keep nitrogen compounds under control and to keep your Oscar Fish tank clean and clear you should have a good filtration system in place.

Beneficial bacteria help to keep harmful nitrogen compounds in control.

These beneficial bacteria form their colonies in the substrate and in the filter of your aquarium.

So you should use a large canister filter and a HOB filter in your Oscar Fish tank.

It will provide a sufficient space to form healthy colonies of beneficial bacteria that will help to keep nitrogen compounds under control and keep your tank clean and clear.

You should also follow best practices while cleaning the filters.

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Water changes

Doing water change is very important to maintain ideal water parameters in your fish tank.

Water change helps to reduce or increase the temperature in your tank.

It also helps to reduce ammonia in your tank.

Ideally, you should do 20-30% water change twice a week.

But if you have a large tank then doing water change once a week is sufficient.

Oscar Fish can get very big and they can be very messy i.e. they produce a lot of waste.

This waste gets converted into nitrogen compounds like ammonia, nitrate, and nitrite.

So if you have a large tank then these harmful nitrogen compounds will get diluted.

But if you have a small tank or if you have overstocked your tank then nitrogen compounds levels can spike pretty quickly.

So, in that case, you will have to do water changes more frequently.

Oxygen

Fish require oxygen to survive in fish tank. So you should make sure that your tank contains optimum oxygen levels.

There are a few signs that suggest low oxygen levels like the fish coming on the surface gasping for air, rapid gills, fish moving around less.

If you noticed any of these signs then you can use these ways to increase the oxygen levels.

Algae

To keep algae in control and maintain a clean and clear tank, you should introduce algae eater fish in your tank.

Usually, algae eater fish like Pleco are bottom dwellers so they can be good tank mates for Oscar Fish and they will help to keep algae in control in your tank.

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FAQ

Do Oscar Fish get lonely?

Oscar Fish usually don’t get lonely and can live happily on their own.

But Oscar Fish have personality and you should try to keep at least a pair of Oscar Fish to promote social interaction.

You can also keep other species of fish like Plecos, Silver dollars, other cichlids like Convict cichlids, Firemouth cichlid, etc with your Oscar Fish.

Can you keep Oscar in a 10 gallon tank?

No, you should not keep Oscar Fish in a 10 gallon tank.

When Oscar Fish are juveniles (about 1 inch) they look very cute and little fish.

But Oscar Fish can grow very fast. It can grow at a rate of 1 inch per month.

And in captivity, it can grow up to 13 to 14 inches.

So ideally, you should keep a single Oscar Fish in at least 55 gallon tank.

What fish can live with Oscars?

When it comes to tank mates for Oscar Fish there are a couple of things you should keep in mind.

Oscar Fish can be very aggressive and it will eat anything that can fit into its mouth.

So you should choose the fish that are large in size and that will not fit into the mouth of your Oscar Fish.

Secondly, you should choose the fish that are semi-aggressive and can hold their own against Oscar Fish.

Some good examples of Oscar Fish tank mates are Convict cichlids, Firemouth cichlids, Silver dollars, Silver Arowana. Pleco, etc.

oscar fish tank mates

Can you keep Oscar in a 20 gallon tank?

No, as mentioned earlier, Oscar Fish can get pretty large and it grows very quickly. So ideally, you should keep a single Oscar Fish in at least 55 gallon tank.

What size tank do I need for 2 Oscars?

Oscar Fish can get very big.

It can and get as big as 13 to 14 inches in captivity.

Also, Oscar Fish is a very messy fish i.e it can produce a lot of waste.

For a single Oscar Fish, you should get a 55 gallon tank.

And for two Oscar Fish, you will require 75 to 85 gallon tank.

A simple rule of thumb to follow is to get a 55 gallon tank for your first Oscar Fish and then you should add extra 20 to 30 gallons for every new Oscar Fish.

Can you put 2 Oscars in the same tank?

Yes, you can put 2 Oscars in the same tank.

It is actually recommended to keep at least two Oscar Fish to promote social interaction.

The only thing you should keep in mind is that you should use at least 75 to 80 gallon tank because Oscar Fish can get very big.

How big will an Oscar can get in a 55 gallon tank?

In a 55 gallon tank Oscar Fish can get up to 9 inches.

Oscar Fish can grow larger up to 20 inches if you provide it larger tank.

If you are keeping small juvenile Oscar then a 55 gallon tank is fine for 1 year.

Then its growth will be stunted and you will need to upgrade the tank.

When it comes to tank size for Oscar Fish the more the better!

The bigger the tank, the larger it will grow.

How many Oscars can I keep in one tank?

You can keep as many Oscar Fish as you want in one tank but you have to provide it sufficient space to swim.

For a single Oscar Fish, you will need a 55 gallon tank. And for every new addition, you will require an extra 20 to 30 gallons.

Can I keep to Oscars in 75 gallon tank?

Yes, you can keep to Oscars in a 75 gallon tank if they are small in size i.e. less than 10 inches.

If you got larger Oscars then you will have to upgrade the tank to at least 125 gallons.

Can you keep an Oscar in 55 gallon tank?

Yes, you can keep an Oscar Fish in 55 gallon tank.

However, after some time its growth will be stunted once it reaches 10 inches.

Oscar Fish can get pretty large and it can grow up to 20 inches. So for further growth, you will need to keep it in a large tank.

Conclusion

So this is everything you need to know about Oscar Fish tank size.

I hope now you don’t have any confusion about Oscar Fish tank size.

If you have any doubts or questions let me know in the comments.

As always, happy fish keeping!

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