Most people see a Oscar and think it would make a great fish for their 10 gallon tank. Most people are unware of how large this type of fish will grow and even when listed for 10 gallons they will shortly outgrow this. Most oscars require a solitary life in a 90 to 100 gallon tank. If you plan on having three Oscars (two Oscars are typically not a good idea) you will need closer to a 150 to 200 gallon tank.Oscars are a tropical fish and prefer their water temperatures to be in the mid seventies so a water heater or two is a must. The @@AMAZONTEXT;B000SSCT3A;number of heaters@@ you require will depend on the tank size. You may have to purchase two heaters to get the temperature correct. You will also have to plan on purchasing a nice canister filter. The hang on back filters will not do it for an oscar. They are a very dirty fish and a messy eater to boot. You will most likely want to over filter the tank then under. If you have a 100 gallon tank plan on getting a filter for the next size up, for example a @@AMAZONTEXT;B000I1O2PK;150 gallon tank or higher@@. You need to make sure you have a good biological filter going with an oscar. Oscars typically prefer drift wood and rock decorations over real or plastic plants. They tend to like to rearrange plants which make a bare tank or one filled with things that are unmovable, prefferable. When possible go with a fine rock substrate over the larger washed river stone. This is because oscars love to be able to move the bottoms of their tank around as they desire. If you are considering purchasing an oscar, it would be highly recommended to do some research on them as there are a few things that are a bit unique to this cichlid. A great book to consider is @@AMAZONTEXT;0793837626;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.