Oscar fish are a widely popular species of freshwater cichlid. They are known to be very interactive compared to many other fish and are commonly referred to as the “dogs” of the aquarium hobby. They come in a variety of colors and patterns, many of which are truly spectacular.
This guide covers everything you need to know about Oscar cichlid care, feeding, breeding, and more. These fish make incredible pets, so let’s get started!
About Oscar Cichlids
|Common Name||Oscar fish, Oscar cichlid, Marble cichlid, Velvet cichlid|
|Scientific Name||Astronotus ocellatus|
|Origin||South America, Amazon and Orinoco rivers|
|Size||10″ to 14″|
|Tank Size||75 gallons for juveniles, 125-150 gallons for adults|
|Food||Omnivorous (cichlid pellets are a good choice)|
|Water pH||6.0-8.0, but do best in pH of less than 7.5|
|Tank Mates||Usually a solo fish, but can live with other large cichlids|
|Breeding||Relatively easy besides the need for a large tank|
Oscar Cichlids are often given a very bad rap as an overly aggressive fish. This isn’t always the case; Oscars just naturally want to eat fish that are smaller than them. This becomes a problem when they’re housed with small species such as guppies, mollies, etc.
Since Oscar cichlids get pretty big, they can eat most other commonly available freshwater fish. If given enough space, generally 125 to 150 gallons, two Oscars will usually get along well.
Each Oscar fish has a unique personality, more so than many other freshwater aquarium fish. They are interactive, and if you do keep two, you will be able to see just how much personality each fish has. It’s amazing to see the differences and interactions between two fish of the same species!
Oscar fish originate from South America, and more specifically the Amazon and Orinoco rivers. They usually hang out in slow moving areas of the river that tend to stay warm. Oscars do not tolerate cold water, making temperature one of the most important things to look out for when keeping this species.
Oscar fish usually live between 10-12 years, but there are reports of individual fish living up to 20 years. If you’re planning on getting an Oscar, make sure you can keep them for a long time.
Oscar fish usually grow to 10″ to 14″ in captivity. In the wild they can grow even larger, sometime up to 18″ (although this is rare).
Oscar Fish Care
Here are some essential things you should learn before attempting to keep Oscars:
Oscar Tank Setup Overview
While Oscars require large tanks, they are extremely hardy fish and are easy to care for. Most tank mates should be avoided, but an Oscar’s personality can easily fill the empty space.
- Tank Size: Many sources recommend a 55-gallon tank for Oscars, but this does not give them enough room to turn around. A 75-gallon can work for juvenile Oscars but is still a bit of a tight squeeze. A 125-gallon or 150-gallon would be ideal for these fish and is large enough to house two of them.
- Water Flow: Oscars come from slow moving rivers, but they are not picky when it comes to flow rate. They will be fine in low, moderate, and high flow rates, and can often be seen playing in the output flow.
Aquarium Water Parameters
The Oscar Cichlid comes from a softer, low pH area of the Amazon River, but these hardy fish are highly adaptable. Even though they can survive in most water, they do prefer softer, more acidic water.
Basic guidelines for Oscar water parameters:
- pH: 6.0-8.0
- Temperature: 77-80°F
- Alkalinity: 8°-15° dGH
When keeping Oscars, stability is more important than ideal parameters. If your hardness is a bit off, it’s better for the fish to adjust to your water, rather than the parameters changing frequently.
Changes to water hardness, pH, and temperature cause stress to your fish, which can shorten its lifespan.
Oscars, like all fish, are sensitive to ammonia and nitrite, and nitrates. Ammonia and nitrites are extremely toxic and should not be present in the tank at all. Be sure to properly cycle your aquarium before adding an Oscar Cichlid, or any other fish.
Nitrates tend to be more of a problem for Oscar keepers. They build up in the aquarium over time.
Since Oscars are huge waste producers, most owners change their water once or twice every week. Failing to keep nitrates below 40ppm lowers the Oscar’s immune system, and often leads to Hole-In-the-Head Disease, or HITH.
It is extremely important to test your water, and the API freshwater master test kit is the most accurate test kit on the market, and cheapest per test.
Oscar Fish Feeding
Every fish should be fed multiple types of food per week. Oscars are primarily carnivorous, so their diet should be meat based. They need a staple commercial pellet, since these provide necessary minerals and vitamins.
Hikari Cichlid Gold is a good staple pellet for Oscars, and other carnivorous cichlids. They can also be fed beef heart, earthworms, night crawlers, jumbo krill, frozen brine shrimp, and freeze-dried crickets, grasshoppers, mealworms and bloodworms.
Some of these foods, such as bloodworms and beef heart, are extremely fatty and should only be fed 1-2 times a week. Live food such as feeder fish are also acceptable, but avoid feeder goldfish, as they contain too much Vitamin A, which can be harmful to Oscars.
Overfeeding your fish can lead to bloating problems and excess ammonia, nitrite, and nitrate, so it is important not to overfeed your fish. Feed your fish only what they can eat in 15-30 seconds one to two times a day, unless you are feeding live food that must be hunted down.
Oscar cichlids do not school, but if provided with a large enough tank, they will coexist peacefully with others of their species.
Types of Oscar Fish
There are three main types of Oscar fish, but only one is commonly kept. This commonly kept species has over twenty different color morphs, and no one can resist all these colors!
This is the most popular type of Oscar, and these are the ones you see in stores. They come in a massive variety of color morphs, including the Tiger Oscar, Albino Tiger Oscar, Albino Oscar, Red Oscar, Albino Red Oscar, Golden Oscar, Super Red Oscar, and Lemon Oscar. There is also a Blueberry Oscar, but these are a product of dyed fish, which can result in a mortality rate over 90%, and the color will fade after a year. These are the Oscars known for their patterns and personalities.
- Scientific Name: Astronotus ocellatus
- Size: 10-16”
- pH: 6.0-7.5
- Temperature: 77-80°F
These Oscars are extremely rare in the aquarium trade and are often mistaken for their more popular cousin. These fish also produce an extreme amount of waste, so even though they are smaller, they require just as much filtration. They are also extremely hardy and will eat the same food as other Oscars. Even though little is known about this species, they thrive under the same conditions as the common Oscar.
- Scientific Name: Astronotus crassipinnis
- Size: 10″
- pH: 6.0-8.0
- Temperature: 77-80F
Bumble Bee Oscar
This is another rare Oscar species, though not as rare as the Fat Oscar. These Oscars are gorgeous, black with yellow stripes, hence their bumblebee name. They also have a large red “eye” just before their tail, which is a shockingly bright color. Their care is the same as the other Oscars and they can be kept with others of their species.
- Scientific Name: Astronotus orbicularis
- Size: 10-16″
- pH: 6.0-7.5
- Temperature: 77-80°F
Oscar Tank Mates
When choosing Oscar fish tank mates, keep in mind that they will eat any fish smaller than them when full grown. Also, due to their aggressive nature, tank mates should be added to the tank before, or at the same time that the Oscar is.
There is no hard and fast rule when it comes to mixing fish. Some fish-keepers will have success keeping two fish together, while other will not. If you plan on adding anything to your Oscar tank, watch the interactions carefully and separate the fish if you see any aggression.
Suitable Tank Mates
- Other Oscars
- Sailfin Pleco
- Common Pleco
- Green Terror Cichlid
- Jack Dempsey Cichlid
- Other large Cichlids
Tank Mates to Avoid
Here are a few species you should not keep with your Oscar:
- Small Fish: Any fish that has a maximum size below 10” will become a snack as your Oscar grows.
- Invertebrates: Shrimp, snails, and crayfish will be eaten by your Oscar. Some Oscar keepers breed the self-cloning crayfish in order to add some variety to their pet’s diet, and others feed excess livebearer fry.
Oscar Fish Tank Setup Guide
If you’re looking to set up an Oscar only tank, then this section is for you!
- Tank: The best tank size to start off with is a 125-gallon tank. This allows your Oscar enough room to swim around and turn and allows the option to add tank mates in the future. Larger tanks are easier to begin with, since their waste is diluted, and nitrates will build up slower than in a smaller tank. I’ve seen a lot of sources claiming that a 55-gallon tank is suitable for a full grown Oscar – please do not listen to this!
- Filtration: For the large tank size that Oscars require, canister filters are the best option. These will keep large tanks crystal clear and can keep up with the massive amount of waste produced by Oscar Cichlids.
- Heater: A heater is essential to keeping Oscars, because cold temperatures, even room temperature, can be a death sentence. I use a Cobalt Aquatics Neo-Therm and absolutely love it!
- Lighting: This is a personal choice, since Oscars do not have much of a preference when it comes to light. Additionally, cichlids in general love to uproot and tear apart plants, so lighting is not needed for plants, as they often do not survive.
Choosing a Substrate
Oscars are such ferocious eaters that they will sometime root around in the substrate looking for uneaten food that has fallen to the bottom. If you’re using a gravel substrate, pieces can sometimes become swallowed and impacted in their intestines.
If this happens enough, it can pose a huge risk to your Oscar’s well-being. For this reason, I recommend using some type of sand substrate which can pass through their digestive track easier and doesn’t pose the same risks as gravel.
If you plan on using same, be aware that eaten sand can sometimes cause their feces to become white and stringy, which is often confused with internal parasites.
Aside from sand, some people use plain tile as a substrate, which is easy to clean around.
Your last option (and my favorite) is a bare bottom tank. Bare bottom tanks are extremely easy to clean, which is a big plus when it comes to messy fish like Oscars, but it is not the most aesthetic option.
Adding Live Plants
Live plants and Oscars do not mix, as Oscars love to destroy them. It is nearly impossible to get plants to thrive when surrounded by these fish. Alas, if only we could combine the stunning Oscar and beautiful planted tanks!
Rocks and aquarium driftwood can still be used as hardscape, though Oscars may move smaller rocks and light driftwood around.
Cycling Your Aquarium
Oscars are extremely sensitive to ammonia and nitrite, so it is essential to cycle your aquarium before introducing any fish. Even though you must wait to add fish, there is no need to wait to add the hardscape. This is your time to set up the aquarium exactly to your liking before adding fish.
This essential cycling time not only allows you to set up your perfect hardscape, but it also allows you to research everything you need to know about your planned pet. Additionally, it allows other types of bacteria and biofilm to establish, which leads to an overall healthier tank.
Oscar Fish Breeding
After keeping Oscars and experiencing their personalities, some owners want to take their love for Oscars to the next level by breeding them. Some owners who keep a pair of Oscars may simply come home and find that they own a perfect breeding pair.
The Breeding Setup
Breeding Oscars can be a daunting task, despite the fact that they are beginner fish. Startup costs can be high because of the tanks and materials needed.
Oscars can have up to 3,000 fry in one spawn, which will require hundreds of dollars’ worth of tanks, heaters, filters, air pumps, manual labor, and other equipment.
Once a pair bonds, there isn’t much that will stop them from spawning. This is not meant to discourage anyone from breeding these magnificent fish, it is only a warning.
- Strategy #1 – Dedicated Breeding Tank: Setting up a tank aside from the “main” or “display” tank is the first option. This includes getting a new tank, heater, and sponge filter(s) depending on the tank size. These need to be purchased either way, since a large adult female Oscar can lay 3,000 eggs, and multiple grow out tanks will be necessary. In this case, instead of removing the fry from the tank, the adults will be removed instead. This option is more commonly used when the adults are separated from one another, either for conditioning or other reasons.
- Strategy #2 – Dedicated Fry Tank: Since Oscars are commonly kept in male/female pairs in the main tank, it may be easiest for most to simply add in a flat breeding surface, condition them, raise the temperature, and wait. Once the fry are grown enough to be moved to a fry tank, they can simply be siphoned out, which is the most common practice. This is also the circumstance for accidental breeding, which occurs when someone purchases two Oscars as companions and they end up forming a bonded breeding pair.
The second option is the one most commonly chosen for Oscars, since they generally don’t have tank mates that will stress the pair or damage the eggs. Additionally, it is less stressful for the parents since they are not being moved from tank to tank.
Setting up a Fry Tank
Fry tanks, especially for waste producers like Oscars, are typically bare bottom for ease of cleaning. They need a heater to keep the water between 77 and 80 degrees and a sponge filter to keep the tank cycled.
The sponge filter is the safest filter for fry, as other filters, such as hang-on-back and canister filters, can suck fry into the filter and grind them up in the impeller or coarse sponge. Sponge filters also keep particles of food that the fish miss within reach, so you will probably observe several fry pecking at the sponge filter 24/7.
Fry will die if there is any ammonia or nitrite present, and they are more susceptible to nitrate poisoning than the adults, so the nitrates should never go over 10ppm in the fry tank. Aside from this, the parameters of the adult tank and fry tank should be identical.
The size of the grow-out tank will vary depending size of the spawn, which can be between 50-3000 fry. Tanks between 20 gallons and 150 gallons are often used, though some standby tanks are needed as fry grow.
Oscar fry tend to grow at different rates. As a result, smaller fry might need to be kept in a separate tank to avoid becoming a snack for the larger fry.
This is another bonus to keeping all of your tanks with identical parameters; no acclimation is needed for the fry, which makes moving them one hundred times easier!
The only way to determine the gender of your Oscars is the breeding tubes, which only appear right before and during spawning. The females have a stubby breeding tube that is flat at the end and very wide. The males have a thin breeding tube that is pointed at the end.
Sexing Oscars is very similar to sexing angelfish, which more people have experience with. Since the tubes are only seen during the spawning process, it will be nearly impossible to go to a store and purchase one male and one female Oscar, especially if they are juveniles.
Buying a proven breeding pair is often cheaper than trying to produce a pair yourself. Oscars take at least 14 months to reach sexual maturity, but some young Oscars will refuse to breed for the first three or four years of their lives.
When taking into account the amount of food and time you would have to put into raising multiple juveniles, the proven pair is often the less expensive option.
Conditioning Your Fish
The typical conditioning period for fish is 1-2 weeks. Best results are achieved using live food such as feeder fish (guppies, rosy red minnows, and other livebearers provide the most nutrition), earthworms, shrimp, snails, and frozen food grade shrimp and fish.
During this period, the male and female should be separated, fed 3-5 times daily, then introduced to one another in the breeding tank. However, it is possible to keep the parents together during this period without separation. The female should be fed more heavily than the male in order to promote proper egg development.
The temperature should be raised between 82- and 85-degrees Fahrenheit in order to trigger spawning behavior. The parents will need some kind of flat surface to lay eggs on, and flat tiles or slate slabs are often used. Their colors will intensify, and their breeding tubes will drop right before they spawn.
Caring for the Eggs
Both parents will vigorously guard the eggs from potential predators, and unfortunately, that includes you. Avoid checking on them too regularly, as they may feel threatened and eat the eggs/fry. The female will fan the eggs to prevent fungus growth, as well as remove the unfertilized eggs by eating them.
Around 4 to 7 days after laying the eggs, the adult Oscars will build a pit in the substrate and move the fry there. It takes around 10 or more days after being laid for the fry to truly become free swimming.
At this stage, the fry can be removed by siphoning them into a bucket and transporting them to a different tank with the exact same water parameters.
At this point, the fry can be fed baby brine shrimp, which are easy and cheap to hatch. They can be fed these alone for the first 1-2 weeks, but other food should still be added.
Blackworms and white worms are a good addition between weeks 1 and 3, depending on how fast the fry are growing. After the third week, the fry should accept ground up flake food and powdered fry food.
Large fry will eat smaller fry, so it is important to move the larger fry to a larger grow out tank. Before you get worried about a never-ending amount of tanks, Oscar fry can be sold at a small size, as small as 1”.
Is an Oscar the Right Fish For Me?
Oscars definitely aren’t for everyone – they’re big, aggressive, and tend to dirty up a tank quicker than just about any other freshwater fish out there. Unfortunately, a lot of big-box pet stores sell baby Oscars that are just 2 to 3 inches without educating customers on how the fish will grow. Oscar fish sell great because they’re entertaining, interactive, beautiful, and affordable.
If you’re a brand new fish-keeper and you’re just coming home from the pet store with your Oscar, make sure you know what your getting into! You should be prepared to upgrade your tank as your fish grows (potentially up to 125-150 gallons) and keep them for 10 to 12 years. If this sounds like too much to handle, you can bring your fish back and swap it for something a bit more practical.
That being said, I definitely don’t want to make it seem like Oscars are impossible to keep. In fact, they’re actually pretty easy as long as you don’t mind keeping a massive aquarium. They’re one of the most rewarding fish to keep and form bonds with their owners unlike any other freshwater fish on the market.