Oscar Fish And Goldfish: Can They Live Together?

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Once I started my Oscar fish tank, I kept asking myself which species could actually share the same aquarium with them. I knew about their aggressive tendencies and didn’t want to sacrifice innocent fish. That was when I started researching whether or not Oscar fish and Goldfish can get along. 

Raising Oscars with Goldfish is highly not recommended. Since Oscar fish are relatively large and aggressive, they are very likely to attack Goldfish, particularly the young ones. Also, Goldfish and Oscars thrive in different water conditions.

As we move forward in this article, I will share with you a video that emphasizes the danger of putting Goldfish in an Oscars tank. Also, I will show you what other fish pose a threat to Goldfish, so you don’t make the wrong decisions.

Also Read: 19 Great Oscar Fish Tank Mates

Can Oscars Live With Goldfish?

People enjoy keeping Oscars because they are undoubtedly beautiful. However, anyone that has ever raised them will tell you that their size and personality tend to complicate the process of finding suitable tankmates. 

To maintain the peace in an Oscar tank, you should find fish that are neither bigger nor smaller than the Oscar. Because Oscars have aggressive personalities, a larger, more robust fish will hurt them. On the other hand, they will attack and possibly even consume any smaller fish that you add to their tank. 

The temperaments of their tank mates are just as important. Obviously, you should avoid aggressive fish. However, passive fish are just as problematic. An Oscar will make a passive tankmate’s life miserable. Therefore, you should find a delicate balance. 

The best tankmates for Oscars should be non-aggressive but also firm enough to stand up to your Oscar if it starts causing trouble. In that regard, it is easy to see why some people choose to pair Oscars with Goldfish. Not only are they comparable in size, but Goldfish are not necessarily pushovers. 

That being said, unless you have no other option, Goldfish are not suitable companions for Oscars. The two can live together under certain circumstances. But in an ideal situation, you are better off finding the Goldfish a less aggressive tank mate. 

To better understand why these two creatures are not suitable companions for one another, consider the following:

1. Size Differences

Fish are not the most intelligent creatures where their food is concerned. In other words, they will eat anything that can fit in their mouths. This is why Oscars are such a risk whenever you pair them with smaller fish.[1]

Not only do they grow to a size of 12 inches or more, but they also enjoy eating smaller fish in the wild. As a rule of thumb, any Oscar you add to your tank is likely to eat any other fish that is half its size or smaller. You should always keep that in mind when scrutinizing potential tankmates. 

Fortunately, Goldfish have an average size of 8 inches. The average adult goldfish is too big for an Oscar to eat. However, some Goldfish are much smaller than that. In such cases, they ran the risk of being eaten by your Oscars. That is particularly true for Goldfish that are spawning young, vulnerable offsprings. 

  • If that hasn’t convinced you, here is a Youtube video that says it all. Even though it’s cruel, some fish owners actually feed their Oscars with Goldfish. That could just as quickly be the case if the two species share the same tank:

2. Tank Size Requirements

Goldfish require a tank of at least ten gallons. Oscars, on the other hand, require a minimum of 55 gallons, though you are better off aiming for 100 gallons. Because Oscars and Goldfish are large, you need an equally large tank to contain them.

The easiest way to attract trouble in a tank with Oscars and Goldfish is to overcrowd them. Luckily, most aquarists understand the importance of giving their Oscars and Goldfish as much space as possible, especially in light of the known Oscar’s territorial attributes.

If you are keeping your Goldfish in a relatively small tank, do not attempt introducing Oscars to it. That may end up with a disaster. However, you could consider adding a couple of Goldfish to an Oscars tank, which is probably quite large. 

3. Water Requirements and Waste

The considerable large size of the Goldfish is not a sign that it could inhabit the same waters as an Oscar. Even though Oscars and Goldfish can survive in the same water, it wouldn’t be a comfortable coexistence. 

Oscars require temperatures ranging from 75 degrees F to 81 degrees F. Also. The pH should fall somewhere between 6 and 8. With Goldfish, the pH isn’t an issue. They thrive in conditions ranging from 7 to 8.4. However, complications start to arise once you look at the temperature.

Goldfish prefer temperatures ranging from 68 to 74 degrees F. These figures tend to vary with each type of Goldfish. Some species prefer temperatures ranging from 60 to 70 degrees F, for instance. Still, in an ideal situation, you should keep the temperature between 65 and 68 degrees F. 

As you can see, those figures differ somewhat from the temperatures that support the development and survival of Oscars. In fact, the ideal temperature for an Oscar is 77 degrees F.[2] Unfortunately, Goldfish do not appreciate water that warmth. 

If temperatures exceed 74 or 75 degrees F, the Goldfish will start struggling with oxygen deprivation.[3] If these high temperatures persist, the health of your Goldfish will suffer. The creature’s immunity will deteriorate, and it will become more susceptible to diseases and infections.

Actually, your problems don’t end here. Oscars are somewhat challenging because they are messy fish that produce a lot of waste. Hence, maintaining the quality of the water in their tank tends to present a challenge.

Unfortunately, Goldfish are also quite messy. If the presence of Oscars makes the maintenance of your tank difficult, adding Goldfish will make things much worse. That requires a lot of attention from the fish owner’s side. 

In fact, the chances of a beginner to successfully maintain a tank with both Oscars and Goldfish are pretty low. It takes a lot of experience to keep the water clean and to control the concentration of toxic elements like ammonia and nitrates. 

4. Aggressive Behavior

Goldfish are quite peaceful creatures with a social personality. For that reason, they need equally social and calm tankmates.[4] They are unlikely to thrive in tanks filled with aggressive fish. 

Oscars, on their hand, are not schooling fish. They can survive on their own in a tank. If you must pair them with tankmates, other cichlids are your best options. Otherwise, their territorial nature makes them a danger to smaller fish. 

Oscars do not have the temperament to live peacefully with Goldfish. Even if your Oscar cannot eat your Goldfish, it will probably nip at the creature. If this sort of bullying persists, the health of your Goldfish will deteriorate.

Keep in mind that some Oscars are shockingly docile and will probably live side by side with Goldfish. But these are rare. They are the exception rather than the rule. It is also possible for a young Oscar to ignore the Goldfish that share its tank for a time. 

But once its size exceeds that of the Goldfish, it will probably become an aggressive bully. If that eventually happens, you are better off moving the Goldfish to a separate tank. That might be the only way of saving its life.

How to Make Oscars and Goldfish Coexist?

As was mentioned above, Oscars and Goldfish should be kept away from one another. If possible, you can keep the Oscar singly. But if you are determined to keep Oscars and Goldfish together, these are just a few of the steps you can take to keep the peace between the creatures:

1. Avoid Overcrowding

This goes without saying – you have to avoid an overcrowded tank. Keep in mind that Goldfish need at least 20 gallons of water. Oscars, on the other hand, require at least 55. If you are raising them together, you will probably need a tank of at least 100 gallons.  

Ensure that the tank housing your Oscars and Goldfish is large enough to award the fish ample space to pursue their regular activities without bumping into one another unnecessarily. 

It is also worth noting that small tanks are more difficult to maintain.[5] That is because it doesn’t take long for the concentration of waste to spike. Also, fish tend to get aggressive when they are exposed to poor water quality.

Because Oscars and Goldfish are so messy, you need to provide them with the most massive tank you can get. That will allow you to control the quantities of waste they produce. Otherwise, your fish are going to protest. Naturally, the Oscars will turn their attention to the Goldfish.

2. Feed Your Fish Properly

Don’t let your fish starve. Aggressive species like Oscars are always challenging because they will consume significant quantities of the food you add to their tank. By doing that, they are forcing their more passive tank mates to starve.

However, that isn’t as big of an issue with Goldfish because they can survive on small amounts of food (you are more likely to over-feed them by accident).[6] Your biggest concern is actually the Oscars. If you fail to satisfy their appetite, they will turn their aggression towards their tank mates.[7]

3. Introduce Hiding Places

The easiest way to keep the peace in a tank with aggressive fish is to add plenty of hiding places. However, keep in mind that Oscars tend to rearrange their territories as they see fit.[8] Their large fins and mouths are strong enough to move objects from one place to the other.  

This is why I suggest adding relatively large plants and heavy decorative items that they cannot move. Then, your Goldfish will be able to use these hiding spots to stay out of your Oscar’s line of sight. That could reduce the violent occurrences in the tank significantly.

Also Read: Can Oscar Fish Live With Turtles?

What Kinds of Fish Eat Goldfish?

While Oscars are not suitable companions for Goldfish, they are not the only tank mates you should avoid. Some other fish that would make terrible companions include:[9]

  • Plecos – Common Plecos are a danger to your Goldfish. They will quickly suck the slime off the Goldfish. This, in turn, will make them susceptible to infections. Even though they cannot eat your Goldfish, common plecos are still a considerable threat.
  • Cichlids – Cichlids are predators. They are also quite aggressive. Because so many of them are relatively large, they might create the sort of hostile environment in the tank. That will make your Goldfish miserable. If they are large enough, they might eat the Goldfish outright.
  • Mollies – These tropical fish also have a reputation for being aggressive. Indeed, they are violent enough to attack Goldfish. Their swift movement could make your Goldfish’s life miserable.
  • Corydoras – Corydoras are not just aggressive. Like common plecos, they will remove the Goldfish’s coat of slime, exposing the fish to infections. That is a severe threat, particularly in small tanks.
  • Bettas – Here is another example of an aggressive species that will probably attack your Goldfish. The continuous fins nipping will expose your fish to infections that might eventually kill them. 

Also Read: Oscar Fish And Bettas: Can They Live Together?


While Oscars and Goldfish can potentially live side by side, raising them both in the same tank could pose a challenge. The two key factors here are different water requirements and size differences.

However, if you are determined to make them get along, your first consideration should be the tank’s capacity. Get yourself a large aquarium, perhaps 100 gallons, and more. Anything below that would create a stressful environment.

I hope my article had answered your question. If you got any hesitations or thoughts, feel free to contact me in person. I will do my best to get back to you as soon as I can. 


  1. https://www.thatpetplace.com/articles/oscars-article
  2. https://www.firsttankguide.net/oscar.php
  3. https://www.firsttankguide.net/goldfish.php
  4. https://www.aqueon.com/information/care-sheets/goldfish
  5. https://www.cuteness.com/article/keep-goldfish-biting-other
  6. https://thegoldfishtank.com/
  7. https://pets.thenest.com/stop-tiger-oscar-fighting-other-fish-3821.html
  8. https://www.fishkeepingworld.com/oscar-fish/
  9. https://aquariumadviser.com/what-fish-can-live-with-goldfish/