Oscar Fish Care – The Ultimate Beginner Guide For This Magnificent and Intelligent Fish

Species Summary

Appearance

How big do Oscars get?

The first thing to understand is how large they get. The can grow to be 18 inches long and weigh in at 3.5 pounds (1.6 kilograms) in a home aquarium. In other words, This a big fish.

Young Oscars

Juvenile Oscars are usually white and dark brown, and with white spots on the head.

Color Changes at Will

Not often mentioned, but mature Oscars are able to change scale color when fighting or breeding. This is a common trait of South American Cichlids. They can “color up” when they want or need to.

The “Tail Eye”

Wild Oscars also have a circle of light colored scales near the tail. Theory is that the circle of scales looks like an eye. This eye confuses predators, usually piranha which live in the same environment. It’s possible that the predators are tricked into thinking they are taking a bite out of the body of the Oscar. Instead they might get a nibble of a tailfin.

Behavior & Temperament

Behavior and Interaction with other fish and potential tank mates.

Oscars are a rather aggressive and territorial species. Be aware of this in choosing the tank size and tank mates. My one try at Oscars I was awoken at 3:00 AM by my new Oscar fighting with the other large fish in my living room aquarium.

Taking this into account and their large size, make sure you have a tank large enough for the Oscar and their tank mates.

Interactions with the owner

Oscars are one of the most intelligent fish in the hobby. As I mentioned earlier your Oscar may end up feeling like a pet, rather than a fish. This is because they will interact with their owners even to the point of watching the owners as they move around the room where the aquarium is located.

Here are a few posts from Reddit r/aquariums about Oscar behavior:

“You have an Oscar. There’s your problem. Just make sure he can’t get the cat.”

“I love my Oscar. His personality is closer to that of a dog. During feeding time he would come to the front of the tank and almost way like a dog for food. He would eat out of my hand and was a joy to keep.”

Video: Petting my Oscar Fish https://www.youtube.com/watch?v=kmmGAlzfvv4

Are Oscars Difficult or Easy To Care For? 

They are about as easy to care for as any other South American Cichlid. This means they are fairly hardy but if neglected they will become sick and if uncared for they will die. 

Because of their size they are a little more challenging to care for than smaller fish.

Oscar Tank Maintenence 

As mentioned at the first part of this article is that Oscars are not easy fish to take care of. That’s mainly due to their size. A 16 inch aquarium fish is huge, which leads to buying a huge tank, dealing with huge poops, feeding huge amounts of food, and doing huge numbers of aquarium cleanings.

Of course there is also the huge costs to get started. An inexpensive 90 gallon aquarium and stand, bare, could cost $1,000 or more. When buying the rest of the set up for the Oscar Fish tank a cost another $1,000 is not out of the question.

All done to keep your Oscar healthy so it can live a normal life span.

Let’s dig a little deeper…

Besides tank maintenance, there are a few other factors which govern the health of your Oscar fish. These are all factors which you control.

As mentioned, water quality is an important factor in keeping Oscar fish. The closer you can get to the conditions in the Amazon River Basin waters, the less stress your fish will have. This means your Oscar will be better able to fight potential disease.

Aquarists have a small amount of control over the water hardness. I use a reverse osmosis water filter to remove minerals in the water that I use when cleaning my fish tanks.

I know that feeding fish (fish foods) adds minerals back into the aquarium water. This is part of the reason to do water changes on a regular basis. By regular I mean massive water changes of 50% or more, done weekly or more often.

I use reverse osmosis water as the replacement water so that I can start with water that is very low in minerals.

Essential Water Conditions

You decide to buy an Oscar because it’s small and cute. You take it home and put it in a 55 gallon aquarium with your other community fish. Six months later, you notice that it is getting easier to keep your aquarium clean. That’s because every few days you have one less fish in your tank with your now eight inch Oscar.

Six months after that, you have no community fish and a 12 inch Oscar laying on its side dying because the tank is too small for such a large fish.

While you can’t force a dying Oscar to get better, you can take steps to ensure that this doesn’t happen.

The most important idea I can convey to you is how large of an aquarium you will need for your 14, 16 or 18 inch Oscar.

I certainly wouldn’t go smaller than a 90 gallon tank. 90 gallons is barely big enough for such a large fish. If I had the money, I would probably aim for a 150 to 200 gallon tank.

Why would I suggest this size tank? Two reasons actually: 1. You don’t want your Oscar stressed out because its tank is too small. Stress kills fish fairly quickly. 2. A large tank won’t have large fluctuations in water parameters.

It’s fairly easy to figure out what water conditions or parameters an Oscar Fish needs. They are native to the South American Amazon River Basin.

Water Temperatures

First off, the water temperatures need to be fairly consistent. Suggested temperatures are 75 degrees F (24 degrees C) and up to 82 degrees F (28 degrees C) on the upper end. I try to keep my aquarium water temperatures around 78 degrees F. I try not to do too much adjusting of the heater in the tank. For several weeks now, the temperature in my 30 gallon planted, tiger barb aquarium has been 77 degrees, which is close enough to 78 degrees that I’m not going to mess with that parameter.

Water softness of the Amazon Basin

Amazon fish live in soft water. Water hardness is measured mostly by the amount of dissolved solids in the water. Those solids are usually calcium and magnesium. The numbers are parts per million.

Amazon River Basin fish live in water that is maybe 10 to 30 PPM dissolved solids. This is very soft water. These numbers let you know how hard the water should be for your Oscar. All of this said your Oscar fish can get used to hard tap water.

Water pH

PH is a measurement of acidity of substances (such as aquarium water) on a scale of 0 to 14. 7 pH is neutral. Hydrochloric acid has a pH of .5. Baking soda has a pH of 9.

The dissolved solids in water acts as a buffer against acidity. What this means is that the higher the dissolved solids in water the higher the pH. The less dissolved solids usually means a lower the pH.

Amazon River water has a low pH due to how soft the water is.  Low pH is water that is lower than 7 pH.

So, fish that originated in the Amazon area need soft water with a low pH. Just as an example, Neon and Cardinal Tetras can be found in water that has a pH of 6 or lower. That is very acidic.

So bottom line for suggested water parameters for an Oscar fish is soft water (10 to 30 PPM) and a pH lower than 7. This said they can become acclimated to tap water that has a hardness of 100 PPM, give or take.

Water Filtration

Most hobbyists: 

Filtration is an important part of keeping an Oscar fish tank clean. I will tell you what I suggest and then I will tell you what I would do.

Fish keepers will suggest one large filter to one large fish tank. With a 100 gallon tank, it would be wise to purchase a canister filter that would run the entire water volume of the tank through the filter several times per hour.

What I do (would do) to filter an aquarium:

What I would do is to have at least two large canister filters running 24/7/365. For example, I have a 30 gallon aquarium that has two Fluval 207 canister filters set up. Filtration is measured in gallons per hour. Under the best conditions, each Fluval will pump 206 gallons of water through the filter media or a total together of 412 gallons per hour. This is a “water turnover” of 13.5 times the water volume per hour.

Besides this, I also have a 400 gallon per hour powerhead running near the bottom of the aquarium (no filter). This is to help keep debris from settling on the gravel.

I also have a UV sterilizer hooked up to each of the return tubes of the Fluvals. Having these keeps the parasites, bad bacteria, fungus, and algae in check.

What To Feed Your Oscar

Image above: A plate of crickets

First, I would say that in regards to feeding your Oscar you will want to keep an eye on them after you feed them. It’s quite easy to over feed a fish. If you feed the Oscar and walk away, you won’t know if you’ve overfed or less likely, underfed, your fish.

You will want to feed your Oscar Fish about twice a day. That’s what I my fish and it works for me.

To keep your Oscar healthy you want to provide him or her with a varied diet of processed flake and pellet foods, canned or fresh cooked veggies, frozen foods like brine shrimp, blood worms and frozen feeder mice (when your Oscar is large enough), and live foods like crickets.

Top of the Food Chain: Feeding Oscars in the Home Aquarium – Tropical Fish Magazine

Aquascaping An Oscar Habitat

The best decorated Oscar fish tank set up I have seen is an aquarium with these items:

1.  A very thin layer of large pebbles covering the bottom of the tank.

2.  A bunch of large, roundish rocks piled together that were holding a large piece of driftwood firmly in place. I don’t know for sure, but the rocks may have been glued together. Not a bad idea if so.

This is a set up that, except for the pebbles, the Oscar Fish couldn’t rearrange and it was fairly attractive.

Plants

It is quite possible to have plants in your Oscar tank. But it is also possible that you might get an Oscar that hates plants. From what I’ve seen is that only having one or two plants is a bad idea. The Oscar may beat up the plants because…well, because he’s an Oscar.

I have seen several YouTube Videos that showed planted Oscar tanks. Adding a Mature Oscar to a well planted tank that already has a few other fish in it to distract the Oscar from the plants, makes having a planted Oscar aquarium quite possible. You just have to get the aquarium totally set up ahead of time and make sure that the tank is full of plants.

Are Oscars too much? How about trying Goldfish? 

How I grow large aquarium plants

How to breed Oscar Fish

Like all South American cichlids, breeding Oscars is pretty straight forward. A healthy, well-fed male and female will breed without almost any help from the owner.

Determining which is a male Oscar and which is a Female Oscar

1.  A male will have a slightly rounder head vs the female whose head slopes back with no bump or hump.

2.  Full mature males will be larger than the females. Not by a lot, but noticeably bigger.

3.  Male Oscars will have three darker spots at the base of the dorsal (back) fin. Females just have one large spot and not as dark. This is not always an indication. If the fish is highly inbred, these indicative colors may have been bred out of the fish.

4.  Males will have a small protrusion near the anus. Females will have a small tube near the anus that lies flat against her belly.

Breeding Tank

When that’s ready, place the male and female pair in the breeding aquarium. Feed them a high protein diet, but of course, keep the tank clean. The bottom of the tank should have some gravel as breeding pairs like to dig. I have also seen flat rocks put in the breeding tank as a place to lay the eggs.

Important: Keep the breeding pair by themselves in their own breeding tank. If you leave fish in the tank with them, there is a chance they will kill those fish in their efforts to protect the eggs.

Courtship

The pair of fish will begin courtship by appearing to fight. This activity is open mouthed, pushing against each other.

Egg Laying

They will eventually lay the eggs and fertilize them. The female may lay up to 1,000 eggs. If the Oscars feel safe and the water parameters are near optimum, they will take good care of the eggs by fanning them and then the hatched wigglers.

Eggs —- Wigglers — Fry

When the fry are free-swimming, begin feeding them processed fry foods, cooked egg yolk, and newly hatched brine shrimp. Live daphnia and micro worms are small enough that when the fry are a bit bigger, they will eat that live food as well.

Fully swimming baby oscars

The parents will continue to care for the baby Oscars. Fully swimming fry can be separated from the parents. At that point you can grow out the fry until they are of a sellable size.