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Don’t Be Deterred By This Aggressive Fish – Consider Raising The Oscar

If you have a freshwater aquarium with plenty of caves and rocks, you may have wondered whether there are any new species you can add to your fish tank. While the Oscar Fish is known for being a bit territorial and aggressive, it is nonetheless a fantastic fish that you should consider keeping in your freshwater aquarium.

This fish can be somewhat temperamental, but if you know the unique quirks of its personality, you can care for it with ease. They are omnivores, making them relatively easy to feed, but it can be somewhat challenging to find good tank mates for this fish.


Oscar Fish Background

Oscars Fish

Oscars, also known as Astronotus ocellatus, are a species of cichlid from South America. While some cichlids are native to Africa, these fish are generally found in countries such as Ecuador, Columbia, French Guiana, Brazil, and Peru. Typically found in the Amazon River and its tributaries, this fish makes its home in one of the most biologically diverse areas in the world.

That’s not to say that you won’t find Oscars elsewhere, however. These fish can also be found in places such as China and North America, but they aren’t native to those areas – they were only brought there as a result of the fishkeeping industry.

Oscars are very popular in home aquariums but you should not consider raising a cichlid unless you have some experience in raising fish. They can be somewhat territorial and aggressive, and they have a lot of personality to boot. There are multiple patterns and colors of Oscar fish, and when raised with care, they can live up to twenty years in captivity.

Oscars can be found in most aquarium stores, however, with healthy fish available for purchase at less than $10.

Oscar Fish Appearance And Behavior

Oscars 1
Photo by Rod Golda

There are many types of Oscar fish, but most grow to be exceptionally large – some reach over 12 inches! What’s even more important to note is that Oscar fish grow quickly, often putting on more than an inch a month during the heaviest and fastest periods of growth.

Oscars have long, oval bodies, with anal and dorsal fins that stretch along the body to the caudal fin. This fin forms a well-developed fan at its back. This fish is extremely difficult to sex, as males and females look very much alike. You would need to take a very close examination of the fish’s genitals in order to tell the difference between the genders.

These fish are usually covered in black and orange splotches – most commonly seen in the Tiger Oscar, but these colors do have a tendency to change and evolve over time. There are other varieties and colors of Oscars that have been developed through the process of selective breeding.

Red Oscar Fish and Lemon Oscar Fish have bodies that are either a solid red or solid yellow, but both have white or black fins. You can even find Albino Oscar Fish that are entirely white all over their bodies.

Do not add an Oscar fish to your fish tank without thinking very carefully about it first. These fish can be extremely territorial and won’t be afraid to attack other fish. If a fish encroaches on their territory, they will attack without warning. They can become more aggressive during times of feeding and mating, too.

Otherwise, your Oscar fish will spend most of its days swimming in the middle sections of the fish tank. They may occasionally daft down to the substrate to look for food. These fish are known to uproot decorations, plants, and other items, so you will want to make sure you secure everything in your tank to prevent your Oscars from shuffling it around.

Oscar Fish Tank And Water Requirements

Oscar fish 1
Photo by Bambang 8974

Oscar Fish have evolved to live in their endemic habitats – therefore, you need to do your best to set up a tank that is the most similar to the conditions in the Amazon River. Freshwater rivers of South America tend to be quite warm, and they have a neutral pH that makes them ideal for healthy Oscar Fish.

In your own fish tank, you should avoid extreme temperatures, alkalinity, or acidity. However, it’s important that you make sure the water flow is strong and steady, as most Oscar Fish in the Amazon are used to a heavy current. These waters don’t tend to be crystal-clear, but the water in your own tank should be well-filtered.

You can use any type of substrate, but those that work best include a soft material, like fine-grained sand. Oscars have a tendency to dig, so you want to avoid anything that might scratch them. You can, however, add some vegetation, rocks, or debris to the top of the substrate.

Another good idea is to use a sandy substrate and then scatter bogwood, rocks, and other decorations around the tank. You can form several caves of each fish, too, which will give them somewhere to hide and to defend their territory. This will prevent any issues of aggression from arising within your tank.

As mentioned, Oscar Fish, like many other types of cichlids, like to engage in digging behavior. You need to make sure that all of the decorations you use in your tank are rooted firmly in place and will be able to resist any form of damage.

Live plants are a good choice for an Oscar Fish tank, as these mostly carnivorous fish aren’t likely to make a snack out of them. However, you do need to be careful in using live plants in your tank, as these fish may have a tendency to uproot them as they dig through these substrate. Make sure you select hardy plants, like hornwort. Floating plants in general are usually a good idea for using in an Oscar Tank, because they of course cannot be uprooted.

You can place your Oscar in a tank with a wide range of water conditions, but ideally temperatures should remain stable at a set point between 74 and 81 degrees Fahrenheit. The pH should be between 6 and 8 and the KH should be between 5 and 20.

You don’t really need any particular kind of equipment to keep the water consistent and stable – you will just need a filter to keep things clean and a heater to maintain an ideal temperature range. You can also use practically any kind of aquarium light.

You should also add a filter outlet that produces a strong current. This will eliminate your need to add an air pump or a water pump.

Remember – as with decorations, any equipment that you decide to use in your Oscar Fish tank needs to be rooted firmly down. Otherwise, your Oscar Fish can easily damage it. What’s even worse is that your Oscar Fish may injure himself if he continuously tries to uproot or move your equipment.

Oscar Fish are large species, so they should be kept in aquariums of at least 55 gallons or more. Small tanks can easily stress your fish, which can lead to a variety of problems with their health and with potential aggression. Consider using a tank that is at least 55 gallons for the first Oscar, and then add an additional twenty to thirty gallons for every new Oscar you add on top of that.

What Do Oscar Fish Eat?

Finding companions for your Oscars can be challenging – feeding them is not. These omnivores will eat just about anything you put in front of them, although in the wild they prefer to eat foods like larvae, tiny fish, and small bits of plant matter. They also eat a ton of crustaceans and small insects ,with these foods comprising the bulk of their diet.

When you are feeding an Oscar in the aquarium, your best bet is to use storebought pellet or flake foods. These will have all the nutrition your fish requires in order to be healthy. You might also want to consider adding frozen or live foods, as these are chock full of the protein your large fish needs to be healthy.

There are a number of live foods you can feed to your Oscar fish, but the best diet will have a wide variety of various types of foods to help your fish stay healthy. You could add some brine shrimp, daphnia, or bloodworms. These live foods help encourage your Oscar’s natural tendencies to hunt. You might also add some chopped up green vegetables, which your fish will enjoy eating. These can be fed by themselves or as ingredients in homemade fish foods.

Oscar Fish usually won’t bother you live plants too often. As long as you are feeding them the proper foods, you shouldn’t have to worry about them going after your live plants.

Feed your Oscar fish several times a day. You should be feeding them small amounts that they can reasonably finish within just a few minutes. You do need to keep an eye out for aggressive behavior, as these fish can get quite excited around food and will go into somewhat of a feeding frenzy.

Oscar Fish Tank Mates

If you are looking for a friendly community fish, the Oscar Fish is sadly not the right fish for that job. This species is not great at making friends, possessing an aggressive nature that can cause it to frighten its tank mates. Although they live in some of the most diverse areas of South America and are used to being around other fish, that certainly does not mean they like them!

In a fish tank, this problem is exacerbated because the fish will be housed in such close proximity to each other. You need to do your best to provide the fish in your tank with plenty of space. You should make a point of only keeping large, peaceful fish in your tank, because these animals will be able to get out of the way of the Oscar Fish while also having the ability to defend themselves against territorial attacks.

Avoid small fish or those that are more aggressive. Any small fish will likely become food for your Oscar Fish, and the same theory applies to tiny invertebrates like shrimp as well.

However, there are a number of other fish you can consider. Good options include Convict Cichlids, Green Terrors, Jaguar Cichlids, Severum Cichlids, Sailfin Plecos, Silver Dollars, Jack Dempseys, Firemouth Cichlids, Bichirs, and Arowanas. These fish are all large and peaceful enough to stay away from the Oscar Cichlid. As you can see, many of these are also fellow cichlid species.

You can always keep Oscar Fish with members of their own kind, too. This is usually a safer bet, as your fish are more likely to get along with each other and be able to defend themselves against the attacks of other Oscars. You might want to consider maintaining a very large tank to reduce territorial disputes.

Common Oscar Fish Diseases

Oscar fish 2
Photo by Sasho Popov

Oscar Fish are relatively hardy species, but they do require a significant amount of additional care when compared to your other fish species. For starters, these fish eat a lot because they are so big. They have voracious appetites and will make a lot of mess – they also contribute a significant bioload to your tank.

You should try to perform a water change at least twice a week, but once a week will suffice if absolutely necessary. The more cichlids you have in a tank, the more often you need to clean it. While Oscar Fish aren’t as likely to get sick as other fish species, they can get ill, just like all other animals.

One of the most common diseases to affect Oscar Fish is called hole in the head disease. This disease causes the appearance of sunken areas to form on the Oscar Fish. It might look like cavities and holes on the surface of your fish. Hole in the head is difficult to treat, but it’s usually related to a dietary deficiency. If your fish seem to be getting sick for no apparent reason, consider changing up the diet to add additional or new nutrients to the fish’s diet.

Breeding And Life Spans Of Oscar Fish

Oscar Fish are pretty difficult to breed inactivity. Both males and females can be picky when it comes to selecting a mate, so you can’t assume that just because you have a male and female Oscar Fish in your aquarium that they will automatically breed and produce juveniles. They need to have the perfect match.

You may be able to purchase a breeding pair that has already been established. You can also purchase juveniles, as fish were born and raised together will be more likely to have connections that can lead to the formation of mating pairs.

Unfortunately, this can take some time. Juveniles take up to two years to be fully matured, so you will need to wait for quite some time for the juvenile to mature, pair off, and breed.

However, once the Oscars find their mates, you can breed a number of individuals from multiple varieties. In The wild, Oscar Fish breed during the rainy season. You can mimic the effects of the rainy season in your tank by lowering the temperature of your tank by just a few degrees. You can also sprinkle some water on the surface of the tank and conduct regular water changes every few days. This will help simulate the effect of the rainy season.

When Oscar Fish are preparing to spawn, they will flare their gills and use their fins to signal to their mate that it is time. This signal could be something as simple as vibrations or fin wagging. Once they are ready to mate, the two will prepare a clean rock on which to lay their eggs. Females can produce up to 3,000 white eggs, which hatch within about three days.

Parent Oscar Fish will guard their eggs ferociously until they hatch. After hatching, the females will fan the eggs to prevent the substrate from covering and suffocating them. While the females are doing this, the males will keep other fish away.

Once your fish have hatched, it is time to move the young Oscar Fish to a new tank. This should have pains filter, as another kind of filter can cause the fish to be sucked in and injured. You should feed your young Oscar Fish up to four times a day, which will help them grow and develop more quickly. Move them as they get bigger, or their growth will be stunted by the size of the small tank.

Oscar Fish grow quite quickly, with many growing up to an inch each month until they reach a foot in length. In the wild, these fish grow even larger – some grow up to 18 inches! You can encourage this kind of quick growth by providing your Oscar Fish with plenty of protein and nutrient-dense foods.

When cared for properly, Oscar Fish can live for a long time. In the aquarium, most Oscar Fish live between 8 and 12 years. However, when given the proper care, they can live for up to fifteen years in captivity!

Is An Oscar Fish For You?

Oscar Fish can be challenging to add to an existing tank, since they need very specific (and very large!) tank mates as well as a carefully designed setup. Therefore, you should really plan the rest of your tank around your Oscar Cichlid instead of the other way around.

This likely sounds like a lot of work, but believe us – it’s worth it! This fish is absolutely gorgeous to look at and displays some truly unique social behaviors that you will enjoy watching in your tank. The Oscar Fish could very quickly become your new favorite freshwater aquarium fish – just give it a change.

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