Oscar Fish, Everything You Want to Know Series

Oscar Fish

Photo by: Daniella Vereeken

Oscar fish are extremely smart.  They are know for their aggressiveness so care must be taken in choosing tank mates.  They will grow up 18″ so they need a big tank.  Oscar fish are also know for being messy, so they need good tank maintenance.  Take a look at the other details about the Oscar fish.

Oscar Fish Names:

  • Common: Oscar Fish
  • Scientific: Astronotus ocellatus
  • Varieties: Veil Tale, Tiger, Albino, Red

Oscar Fish General Info:

  • Care Level: Easy
  • Origin: South America
  • Max Size: 15in (38cm) long
  • Life Span: Up to 18 yrs
  • General Temperament: Aggressive
  • Minimum Tank Size: 55 Gallon
  • Tank Region: Entire Tank
  • Preferred Food: Pellets, Freeze Dried, Live
  • Family: Cichlids
  • Ideal Tank Mates: Jack Dempseys, Large Plecostomus, Large Pacus
  • Schooling: It’s best to keep only 1 or 5+.  Anything in between can lead to ganging up one.

Oscar Fish Water Ideals:

  • pH: 6-8
  • Temp: 76°F-82°F (24°C-28°C)
  • Hardness: 5-20dH

Oscar Fish Breeding:

  • Ideal Temp: Warmer 82°F (28°C)
  • Difficulty: Easy
  • Gender Differences: Males colors are brighter.
  • Other Notes: Clean water conditions are very important.

What’s your experience with Oscar Fish ?

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29 Responses to Oscar Fish, Everything You Want to Know Series

  1. Shelleu December 6, 2007 at 9:01 am #

    I have an Oscar fish and he is about 5-6 inches and I have him in a tank with two blood parrots and they get along fine, he has not been aggressive at all, as a matter of fact he tries and stay out of thier way.

  2. Stephanie January 17, 2008 at 8:09 pm #

    I have two oscar fish that are about four inches and some smaller fish that are one inch. I read above that oscar fish are suppose to be aggressive but they are actually being bitten by the one inch fish…

  3. Steve February 12, 2008 at 3:15 pm #

    I have on 4inch oscar and mine has been aggressive towards my 5inch plec. And he is well feed 55g of space.

  4. Nicholas April 1, 2008 at 12:18 pm #

    I have 3 four inch Oscar together with 9 pachu (5-6 inch), 2 Patin and another 4 fishes. as stated above they are extremely smart and good hunter. They get along well with my other fish in the 50 gallon tank. They are big eater and react very fast during feeding this sometime may cause not enough food for their tank mate.

  5. Sarah April 2, 2008 at 8:43 pm #

    I need help with my baby. His name is Rusty and I’m afraid he has HITH, but I’m hoping it’s something else. I’ve removed the activated charcoal, done a water change. He’s still eating, but has had some muscus like stool. I found a little strand in the tank, looked like tomato seeds and some on the charcoal bag from the filter. The wound is on the surface, not pit like, so I’m hoping it’s just a wound that isn’t healing. I’m adding aquarium salt on Friday, unless someone has something else to offer. The nitrates were high so I did a water change today and want to give the tank a chance to settle before adding anything else. I have pictures if someone can help.

  6. Clifford April 3, 2008 at 5:30 pm #

    My Oscar was not aggresive when he was small but now he is very aggresive. He was first in a tank with mollies and guppies and was doing fine at about 2 inches long, but once he got about 4 inches long he is a straight killer now, he ate everything. He even ate my albino black clawed frog which was about 2 1/2 inches long. So he is all by himself now and i think he really likes it. Now he is growing really fast, but of course he is eating a lot: pellets, blood worms, ghost shrimps, and feeder fish, oh yeah and guppies, mollies, and black clawed frogs!

  7. Eric April 5, 2008 at 9:58 am #

    My only other suggestion if you think you are dealing with Hole in the Head is to make sure you have a balanced diet for him. This is generally accepted as the cause for it.

  8. Hevach April 15, 2008 at 11:02 pm #

    The number one rule of an oscar tank is that anything that can potentially fit in its (very large) mouth eventually WILL end up in its mouth. Mine even ate the pleco I kept him with, so I replaced it with a catfish bigger than he’ll ever get, and he leaves it alone. But he’ll eat anything else in the tank – I actually used him to dispose of several tiger barbs that were getting too disruptive for my community tank (Dummies even tried nipping the oscar’s fins, but he didn’t put up with it for long).

    IMO, if you’re going to put one in a tank with other fish, make sure he’s the smallest thing in the tank at any given time, just to be safe. Even the “bigger than his mouth” rule doesn’t always work, as I’ve heard of them trying to swallow fish nearly their own size, even to the point of unhinging their jaw in the process:

  9. Jean May 1, 2008 at 1:24 pm #

    Has anyone heard of oscars changing colors? I have 2 that are the same coppery/green colors and at different times they lose all of the dark green and are totally copper almost gold.

  10. Rebecca July 10, 2008 at 3:50 pm #

    I have an oscar he is big really big anyways i have an eating issue with him I moved and changed tanks same temp all other fish adapted but he won’t eat and keeps changing colors why his he doing this and how do I get him to eat

  11. Justin July 12, 2008 at 3:12 pm #

    i have a few oscars and one really big one.
    they have been going crazy and beating themselves up and i dont know why they are doing it. they wont eat and they randomly flip out and just bash into things. they use to not stop eating but i got some feeders and after that my blue oscar and one of my tiger oscars died and now the others wont eat. does anyone have any idea what it might be??

  12. Justin July 12, 2008 at 3:16 pm #

    if anyone is interested i have two oscars i want to sell i have to many of them 5 actually
    one is 9-10 inches long and hes a beast hes not a tiger oscar he’s got like a red fade color
    the other is about 4-5 inches
    $35obo for the big guy and $20 for the little guy.
    badassjustincp69@aol.com is my email. i live in NH so let me know if your close by.

  13. Eric July 14, 2008 at 6:18 am #

    Color changes are common with stress like tank changes. After the fish get re-acclimated to the tank, you should see the color gradually change back. Not eating can also be caused by all sorts of stresses. If there are no signs of illness and it’s been a few days, I would suggest getting some live food. Feeder fish or live shrimp can many times give Oscars the stimulation they need to get back to normal eating patterns.

  14. Justin July 14, 2008 at 1:48 pm #

    ive tried feeders and he still hasnt touched them and he has no signs of being sick. its been a week maybe more since hes eaten anything. ive tried everything i can think of.

  15. Eric July 17, 2008 at 5:58 am #

    You might mix the food up even more. Try some other types of foods, crickets come to mind as a good choice.
    Also, don’t know if you’ve bread Oscars before, or have male and female in the tank, but your fish could be looking for a mate. Many times during this period fish will put off eating for long periods of time.

  16. junior July 21, 2008 at 5:15 pm #

    man you should see my oscer fish, I went away for a while and left him withe a friend. Now his fins went from black to clear. I think is has to do with the lack of nutreants

  17. Eric July 22, 2008 at 6:31 am #

    I think you hit it on the head. Stress is probably the cause. Good news is that with some new conditions, he’ll quickly change back.

  18. Brent July 22, 2008 at 2:18 pm #

    I have a neat anecdote on my oscar’s behavior:

    A friend of mine moved away and I inherited his fish…

    He had a 4inch oscar and two 3inch parrot fish in a 10gal tank. I knew this was way too small for for these fish so I got rid of the parrots. (Personally, I think they look retarded – and the fish always fought) I figured this as a good intermediate step for tank space until I could afford a bigger tank.

    However, after removing the parrot fish, the oscar seemed DEPRESSED. It may sound ridiculous, but he layed in the corner and wouldn’t eat or even move. He stayed like this for several days.

    I went out and bought a 55gal tank hoping he would recover. Even after several days in this much larger tank he still just lay in the corner on the gravel.

    It seemed like a stretch but I assumed he was just lonely. I bought two 1.5 inch oscars and put them into the tank as well.

    Within 10 minutes he immediately snapped back into action, asserted his dominance and began eating / acting perfectly normal. In the last WEEK he has grown an INCH!

    I don’t know if this is unusual for an oscar but it was definitely new to me as my only other experience with fish has been my koi.

    This oscar has become my favorite pet, and call me crazy but I think he’s smarter than my dog.

    BTW Eric: Great Site! You have a ton of extremely useful information. *Bookmarked*

  19. Todd July 23, 2008 at 6:41 pm #

    I have two Oscars one is black w/orange I have notice in the night it turns gray. They live with two pleco, four tiger barbs, one kissing fish. Let me tell you the kissing fish is the aggresive fish .
    They all eat flakes and dry shrimp

  20. Eric July 25, 2008 at 6:06 am #

    Great story Brent & Todd! Thanks!

  21. rupesh patel July 29, 2008 at 12:37 am #

    i have two Oscars, one is about 6 & other is about 4 inches,what will be proper feed for maintaining there color & health,can i use some veg feed also ? like soybean chunks or some other ?

  22. Eric July 30, 2008 at 8:09 pm #

    Oscars can eat many vegetables including peas, lettuce, spinach, etc. Vegetables should only make up around 25% of their diet though. Here are some more feeding tips. http://www.fishtanktutor.com/the-golden-rule-of-fish-feeding

  23. Rupesh patel July 30, 2008 at 10:11 pm #

    hi Eric,
    thanks for your valuable suggestion about Oscar,but now specifically i want to know about maintaining there color properly.
    what will be perfect diet for Oscar about above matter?

  24. Eric August 6, 2008 at 6:01 am #

    Oscars prefer a high protein diet in general. You’ll want to use a Cichlid pellet as a core food. While vegetables are great, they’ll get their protein from the pellets, live and frozen foods. Bloodworms, feeder fish, and worms are all great choices.

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  26. Cathy July 16, 2011 at 8:00 am #

    it is not a good idea to feed live feeders to aquarium kept oscars as they can cause worms or other parasites to be ingested in the oscars. Flakes, ciclid sticks and shrimp are acceptable. If you run out of food, earthworms are ok, as well as cooked shrimp broken up can be used as well. Just not too much. I had 2 4 inch oscars given too me almost a yr ago and now they are 6.5 inches long. I had them in a 30 gallon but have since moved them into a 55 al. they had a 5 inch pleco with them when I got them but that one died and i replaced it with a 2 inch pleco that is also 7 inches long. They eat out of my hand whenever i feed them. even the pleco does. i just finished a complete deep clean of my tank. and my oscars have never been stressed out. Usually when moving oscars they tend to hide for a few days and not eat. Not mine. As soon as they are in the tank they are ready to be fed. They are fun fish to watch. I had some columbian sharks that were brackish water fish but i was told they could also live in fresh water. they lasted three days. they were only about an 2 inches long and my oscars never bothered them. My oscars have nipped my fingers when ever i had to rearrange the tank decorations or remove one. I have to thump them lightly on the nose then they leave me alone. They do not bother other fish. My oscars are a red oscar and an albino. The albino (nemo) is the boss. The red (ollie) is the submissive one. they are fun to watch when they liplock and push each other around the tank. Anyway oscars are fairly peaceful to other fish as long as the other fish have plenty of hiding spots. just remember do not feed them feeder fish as this will kill your oscars. This comes from a fish store that has been in business over 50 yrs and has NEVER lost one fish due to disease or parasites. Even the ones they sell to customers. So I am inclined to agree with him because I’ve lost quite a few salt water fish some due to inexperience some to to mother nature and power outages.

  27. Eric July 19, 2011 at 6:15 am #

    Thanks for sharing Cathy!

  28. Daniel August 20, 2011 at 10:58 pm #

    Hi Eric,

    You have a very informative site here on just about everything there is to fish. I have a question to ask you about oscar fish, I have 2 tiger oscars (black and albino)and a pleco in a 55 gallon tank. I have read on many other sites that 55 gallons is extremely small for 2 oscars let alone for 1 I was wondering if that is true or not. I have also read that a 30 gallon tank could be suitable for 1 oscar and a pleco. My father had fish all of his life and he said that he had 2 oscars in a 55 gallon tank and they were fine and hardly had any problems with them so hopefully you can answer my question. Thanks

  29. Eric November 8, 2011 at 7:42 am #

    Hi Daniel,

    A 30 gallon tanks is certainly too small. 55 gallon is a minimum. Oscars can grow to be up to 15″ long which would out grow the 55 gallon tank. You’ll rarely see them that big though. With the 1 Pleco and 2 Oscars, a 55 gal usually works well.