A lot of people see a flashy looking oscar and think it would make an awesome addition to their small tank. Most people dont realize how large this fish grows and even if they list them as needing 10 gallons they will shortly out grow this. Typically if you are planning on having an Oscar you will have a solitary one in about a 90 to 100 gallon tank. If you are looking for more than one you should move to three and go with a 150 to 200 gallon tank.
As a tropical fish, they prefer water temperatures in the mid 70s, making water heaters a must. The size of tank you have will determine the number of heaters you need.
You may have to purchase two heaters to get the temperature correct. A nicer canister filter might also be required due to the size of tank. A hang on the back filter will simply not do for Oscars. They are incredibly dirty fish and messy eaters. You will most likely want to over filter the tank than under. Plan on purchasing the next size up filter, for example a 100 gallon tank or bigger.
It is ideal to have a good biological filter going for your oscar.
They also seem to prefer rock and drift wood decorations over plastic or even real plants. Oscars seem to like to rearrange plants if they are able to move them so either a bare tank or a tank filled with things they can’t move may work best. You should go with a fine rock substrate over larger washed river stone when possible. This is due to oscars love to move their tank bottoms around as they wish.
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It is always recommended to doing a bit of research before you purchase this unique cichilid. A great book to consider is Aquarium Care of Oscars It is really important to know what you are doing with this fish because you want them to have a quality life, as they have been know to live for over ten years.