Known for their intelligence, Oscar fish are amoung some of the most popular aquarium fish in the hobby.
And with their ability to recoginze you at their owner, you’ll really want to provide them with the care they need to thrive.
In this guide, you’ll learn everything you need to provide quality care for this intriguing freshwater tropical fish.
Let’s get started.
In the Wild: What are Oscar Fish?
The oscar fish (or astronotus ocellatus, if we’re getting scientific) is a South American species belonging to the cichlid family.
It’s native to many countries, including Peru, Ecuador, Brazil and Columbia.
But to put it simply:
You can find oscar fish pretty much anywhere in the Amazon River Basin.
They typically live in low-flow, slow-moving white waters, which act as perfect hiding spots from predators- especially if there are greenery and branches.
As for their size:
They tend to grow to around 45cm/18in. Not small, ey?!
But even more impressive than their size is the fact that they can grow super fast, sometimes at a rate of one inch per month!
Adults are usually dark in color and spotted with yellow rings on their fins, while young oscars often carry white and orange wavy stripes until adolescence.
But when it comes to baby-making, things are far from cute:
Oscar fish are normally pretty aggressive. But during breeding times? Multiply that by 100.
Breeding makes oscar fish extremely territorial (although to be totally fair to them, I know some humans like that too).
And as for their diets:
They’re known for their voracious appetite and eagerness to consume anything small enough to fit inside their mouths (again, I know some humans…).
Let’s now take a deep dive into the types of oscar fish and how to care for them:
Different Types of Oscar Fish
Oscar fish occur in three different variations: tiger oscars, red oscars, and albino oscars.
Tiger oscars are the most common breed; we generally consider them to be the ‘original’ oscar fish.
You might be wondering, “what do they look like?”:
Tiger oscars have red and orange patterns on top of a dark brown/grey base. They’re pure breeds, and because of this, they possess the true characteristics and behaviors of typical oscar fish.
As for red oscar fish:
You can find them in many different shades, from crimson and copper to rusty orange. Red oscars don’t have the markings or patterns characteristic of tiger breeds.
Alongside tiger oscars, red oscar fish are the most commonly kept breeds.
Last on this list are albino oscars:
Like other albino species, albino oscars are white in color and have shiny, velvety skin and red eyes. And even though they’re different in appearance, albino oscar behavior is very similar to that of tiger and red oscars.
Oscar Fish Aquarium Set Up Guide
Let’s start with the basics:
Oscars are large fish, and on top of that, they’re extremely sensitive to water changes.
Here’s the golden rule:
Your oscar fish will live a long, happy life as long as you make sure your aquarium is suited to their preferences.
Sounds simple, right? Well, it is- as long as you know what their preferences are (duh).
Let’s take a look at each of them in detail:
What’s the Best Aquarium size for Oscars?
Since oscars can grow up to 45 cm, it’s important that your aquarium is large enough to accommodate your pet.
Ideally, your aquarium should be no smaller than 75 gallons.
You could get away with a 55 gallon, but this leaves you no room to add more fish. And, take it from myself and hobbyists, one fish is never enough.
And if your aquarium is too small to house your fish (or overcrowded), it’ll quickly become distressed and unhealthy.
The knock-on effect?
The potential for plenty of nasty, stress-related health conditions to develop, which can end up causing serious harm to your Oscar.
Pro Tip: If you’re buying a brand new tank for your Oscar(s), you can follow this as a rule of thumb:
1 Oscar – 75 gallons
2 Oscars – 125 gallons
3 Oscars – 150-200 gallons
Remember, it’s easier to maintain a healthy environment in a larger body of water because any changes will have less of an impact. These minimum sizes may require maximum effort on your end.
The Best Type of Substrate for Oscars?
When it comes to housing oscar fish, both sand and gravel work well as substrates.
But before you go shoveling the stuff into your tank, take note:
Oscars enjoy digging, as well as taking in and spitting out substrates (like sand). This can cause some filters to break, particularly if your oscar is projecting sand directly at filters (cheeky fella, doesn’t he know these filters cost money?!).
Here’s the solution:
You can incorporate a pre-filter into your tank to prevent any damage from occurring even if you choose to use sand as a substrate.
That way, your oscar can dig up and spit out sand to his heart’s content and you don’t need to buy a new filter every 5 seconds. Win-win!
One more piece of advice:
If there’s any uneaten food or debris in your tank, it’ll sink overtime and work its way into your substrates.
For that reason, you should avoid adding too much substrate, particularly if you’re using gravel (1-1.5 inches is plenty).
As for sand:
Even though it’s finer and way less likely to collect food, you should still use it sparingly.
What Kind of Filtration do Oscars Need?
Oscar fish are very sensitive to water changes and ammonia levels. Because of this, you’re going to need a high-quality filtration system if you want to keep your fish healthy (which, obviously, you do!).
On top of their sensitivity, oscars are also very messy fish and (*prepare for poo talk*) have a large bioload/waste output.
For that reason, oscars need fairly massive amounts of water filtration- with a focus on biofiltration.
Here’s our expert tip:
Your filtration system should be strong enough to turn over the entire volume of your water four times per hour.
How Much and What Kind of Lighting Should I Provide?
Here’s some good news for you:
Oscar fish don’t need any specialist lighting. Simply keeping them in a standard room lit by daylight will work just fine.
But, if you fancy the idea of adding some lights to your aquarium, doing so won’t harm your fish.
Just keep in mind:
Many oscars prefer moderate-low lighting, so you shouldn’t leave your bulb on for more than 12 hours (if you keep it on too long, your fish might become agitated and distressed).
If you have an oscar that shies away when your bulb is on, then you may want to consider dimming your bulb (or removing it completely).
Wondering how you dim the bulb? It’s super simple:
Just poke holes into a piece of tin foil and wrap it around the bulb. The fewer holes, the dimmer your light will be.
Do Oscars Like Plants and Decorations?
As is typical of prey fish, oscars hide amongst objects in the wild in order to feel safe.
Particularly when they’re young, your pet oscars will find comfort sheltering beneath fake plants and ornaments.
Oscars are known for their tendency to rearrange their territories; if you pay attention, you’ll often see them moving small objects around their habitat.
So, what’s the takeaway?
You should probably avoid any breakable decorations, like ceramic objects.
If you have real plants inside the tank, the most likely outcome is that your oscar will tear them up a bit (if not totally destroy them), so fake plants and sturdy decorations like PVC pipes and stone caves are your best option.
Seriously, you’ve gotta prepare for destruction; these little dudes are reckless!
As if that wasn’t enough to keep your hands full:
Oscars are also clumsy; they move around a lot and are constantly bashing into things.
As hilarious as that sounds (and in reality, kinda’ is), there is a serious point to it:
You should probably avoid adding anything to your tank that has sharp edges or rough textures (like volcanic rocks).
One last piece of important info:
Oscars are soft-water fish, meaning they’re sensitive to pH changes and any pH-raising objects. You should avoid adding things like coral, limestone, and any other calcium-carbonate based minerals.
As they are highly sensitive to water changes, it’s crucial that your water parameters are suited to the needs of your oscar fish.
Not only is it harmful to miss these requirements, it can actually end up being fatal.
What Water Temperature do Oscars Require?
Oscar fish thrive in the warm waters of the Amazon River Basin.
Keep your aquarium at around 77 degrees Fahrenheit (25 degrees Celsius), and ideally, make sure it remains between 74 and 81 degrees Fahrenheit (23.5 – 27 degrees Celsius) at all times.
The key is to keep it stable.
How Much Water Flow do They Need?
Oscars love moderate-high flow waters, similar to those of their natural habitat. You should aim to have a water turnover of 4 times per hour.
Got that? I’ll say it again just in case:
Four. Times. Per. Hour.
This might sound like a lot, but oscar fish can cope well with very high water flow conditions. Even if you exceed the stated flow levels you’ll probably find that your pet remains happy and healthy.
So long as your fish is able to swim comfortably, high-flow conditions are totally fine- and often preferred.
What Should the pH, Acidity & Basicity/Alkalinity Levels be?
As always when keeping fish, you should aim to replicate the same water pH in your aquarium that your pets would live in in the wild.
Here’s the key:
Oscar fish prefer a water pH of around 7.2. Your pH should remain stable between 6 and 8 at all times.
Keeping your pH right is very important as it can affect the toxicity of ammonia in your water, increasing the likelihood that your fish will fall victim to ammonia poisoning (we’ll go into this in more detail in the next sections, but for now let’s just say you do not want to see this happen).
If your water pH is too low, you can easily alter it using salts and pH changing kits. But never make quick drastic changes.
You can see how you can alter your pH safely here.
Understanding Chlorine and Chloramines
Chlorine is a big deal for aquarium owners.
Well, chlorine is added to municipal water before distribution in order to kill bacteria.
“So?” I hear you say, “What’s that got to do with my oscar fish?”
A lot, actually! It’s a highly-toxic gas that’s harmful to mammals, amphibians, and fish.
When combined with ammonia, which is also toxic, products known as chloramines will form.
Basically, you can consider this to be an insanely poisonous chemical cocktail which can cause serious harm to your fish.
So, how do you avoid it?
It’s essential that you use a dechlorinator whenever adding fresh water to your aquarium. This will effectively remove chlorine, chloramines, and many other trace metals (like mercury and lead) from the water.
Here’s your golden rule:
Never add water directly from your tap without first dechlorinating it.
As oscar fish are particularly sensitive to water changes, it’s vital that you run your water through a dechlorinator before adding it to your aquarium.
If you’re unsure whether or not you have successfully removed all of these compounds, you can use a simple chlorine test kit to measure your water quality.
Looking at Ammonia, Nitrite, and Nitrate
Most aquatic animals, including oscar fish, produce ammonia as a waste product- which is highly toxic in its unionized form.
Just like the water changes, oscars are very sensitive to ammonia levels, too.
High pH levels force ammonia to remain in its unionized form which, in turn, increases its toxicity. Above a pH of 8, ammonia can become fatal to oscar fish and kill them- fast.
But pH isn’t the only culprit:
Water temperature can also increase ammonia toxicity.
Scary stuff, right?!
So what’s the key to preventing ammonia toxicity from harming (or killing) your oscar fish?
Simple: ammonia tests.
Ammonia kits measure the toxicity levels of your water, and thankfully, you can pick up these lifesaving little gadgets from most retailers.
Unfortunately, though, unionized ammonia isn’t the only thing you need to worry about. You also need to be very careful about nitrite (which is a product of ammonia).
Though it’s considerably less toxic, nitrite (and its byproduct, nitrate) can build up inside your tank- and if it does, it’s going to be bad news for your oscar.
What will happen?
Large amounts of nitrite/nitrate can encourage algae blooms. Some algae species can produce toxins that are harmful to marine life and can lead to disease.
Regular water changes will keep nitrite/nitrate levels down. Easy peasy.
Also, make sure to test your water regularly to ensure that its toxicity levels stay below the safe limits.
In Tank Behavior & Tank Mates
Experts know that oscar fish are mildly aggressive, territorial animals.
Take this as an example:
You’ve got a pair of oscars which you keep in the same tank. You decide that you want to breed them and make little baby oscars- cool, right?
Well, if there are other tank mates in there with them, it’s going to become pretty uncool for them in no time at all.
Because the breeding oscars will become seriously aggressive towards their tank mates during spawning times.
And that’s not the only scenario you need to watch out for:
If multiple oscar fish are sharing a tank that’s too small for them, you’re going to see even more unwanted territorial behavior and fighting. Oscars are known to bully one another, too, and smaller fish are the most likely victims.
Generally, oscars cope best on their own.
You can, however, keep other South American cichlids as tankmates, providing that these fish aren’t too aggressive or too passive (it’s all about balance, man).
I know, I know… It sounds like a fine line.
But here’s the deal:
Aggressive fish will pick on those that are too passive, and a passive fish placed in a tank full oscars will likely be bullied.
And if they don’t get bullied… they get eaten. Yes, seriously.
It’s a fish-eat-fish world out there!
Oscar fish are known for eating anything small enough to fit into their mouth. Guppies and smaller fish are top of the hit list, so best off keeping them separate from any larger oscar fish.
Oscars Diet & Feeding
In the wild, oscars enjoy eating insects, smaller fish, worms, plants, berries- and in truth, they’ll eat any fruit that lands in their habitat.
What Can I Feed my Oscar?
When keeping oscars in an aquarium, you should aim to replicate their natural diet as closely as possible.
Here’s the key:
You should feed your oscar a high-quality, high-protein diet with a variety of processed, frozen and freeze-dried foods.
A high-protein commercial fish food produced for carnivorous species (such as cichlid pellets) will be enough. These should comprise 80% of your oscar’s diet.
You should supplement the rest of your fish’s diet with live, natural food. This may include:
You can also give your oscar dead prawns and shrimp, since they’re both high in fiber and vitamins. But since an oscar’s diet should mainly be made up of lean foods, you should avoid poultry and beef heart.
One last thing to remember:
If you’ve got baby oscar fish, you should only give them small food, to begin with.
How Often Should I Feed my Oscar?
Baby oscar fish are voracious eaters and- like any baby- can seem to be hungry all the time.
But even if they pull the puppy eyes out, you should still limit the amount of food you give them as overfeeding can make them sick.
Here’s how to do it:
1. Start by feeding smaller oscars 3-4 pellets, to begin with. Drop them in, let the oscar eat them, and then add more.
2. Continue this pattern for around three minutes and then stop – only feeding once your oscar has eaten all of the pellets in its vicinity.
3. Repeat this 2-3 times daily, removing any uneaten food from your tank within 2-3 minutes to avoid upsetting water quality.
Your baby oscar may seem full after a feeding session or it may also beg for more. Avoid the temptation to overfeed and don’t give your oscar more than you’re supposed to.
Once your oscar reaches 5 inches, you should change its feeding patterns.
At this point, you should feed them twice daily. You can also supplement larger, living animals like mealworms and grasshoppers during feeding times.
You can continue to feed your oscar fish like this throughout adulthood.
Breeding Oscar Fish
Breeding oscar fish is possible, though it isn’t the easiest of tasks.
Here’s an interesting tidbit for you:
Oscars are actually one of the hardest species to breed.
Why? It’s down to their high standards, would you believe (oscars can be incredibly fussy when choosing mates).
Mates must be mature in order to reproduce; maturity occurs around 16 months – 2 years of age.
You can breed any combination of oscar fish – tiger, red or albino – together.
How to Sex Oscar Fish?
Sexing oscar fish can be difficult. They are monomorphic, meaning that both sexes are virtually identical in appearance.
There are, however, a couple of characteristic features of male and female oscar fish which can be found by looking closely at their genitals.
Females have an egg tube which retracts fully inside of them, while males have a single sharp spike used for fertilization.
Initiating the Breeding Process
In the wild, oscars prefer to breed during rainy seasons.
To replicate these conditions in your aquarium, you’ll need to conduct 20-30% water changes every couple of days.
You can also lower your water temperature by a few degrees to help things along.
Lastly, you can use a watering can to sprinkle ‘rain’ (dechlorinated water) on top of your aquarium for 5-10 minutes a few times per day.
You can also install filter spray bars above your water to replicate these conditions if you don’t actually want to go to the effort of doing it all manually.
Oscar Fish Disease, Illness, and Treatments
Oscar fish rarely get sick, though there are a number of illnesses that they are at risk of catching.
The most common of these is known as ‘hole in the head’ disease.
Errggh… Sounds unpleasant already, doesn’t it?
Well, it is. No two ways about it.
You’ll know your fish has contracted the disease if you see cavities and holes forming across your fish’s head and body.
As freaky as that sounds (and is), it’s also easy to prevent:
Hole in the head disease is commonly caused by nutritional deficiencies in your fish’s diet. By following the dietary guidelines we went through above, you can easily avoid hole in the head disease.
The next biggest culprit is bacteria:
Live feeder fish (such as goldfish) can also cause your fish to fall ill, since they often contain bacteria from settlements.
You should always quarantine feeder fish before adding them to an oscar’s diet if you want to minimize this risk.
More Oscar Fish FAQs
1. How Long do Oscar Fish Live?
2. What do Oscar Fish Eggs Look Like?
Fertilized oscar eggs appear brown/tan in color, while unfertilized eggs are white.
3. Why do Oscar Fish Jump Out of the Tank?
Sometimes oscar fish will jump out of their tanks in an attempt to explore their surroundings or search for food.
Additionally, they may attempt to escape from aquariums that are too small for them.
Keeping a lid on top of your aquarium will prevent your oscar from leaving its tank and coming to harm.
Do you have your own Experiences?
Have your own experience keeping Oscar fish and have anymore suggestions or tips for other aquarists? Let me know in the comments below.
Happy fish keeping.