Before you even look at oscars, you need to have a good tank setup for them. This involves getting a tank that is the right size and one that has good filtration. Having the wrong tank for your fish can lead to illness and will cost you more in the long run. It's best to have your main tank ready before you choose your oscar. They can quickly outgrow “starter” tanks, so start with a full sized tank.
Many oscar experts disagree about the minimum tank size needed for these fish. However, most agree that 55 gallons is the bare minimum you should consider. This size is good for a young oscar, but as they grow they might need a bigger tank so they can more easily move around. Assuming you only plan on keeping an oscar and no other fish, a 75 gallon tank is comfortable for them.
If you plan on having a mated pair of oscars or plan on introducing your fish to other tank mates, you'll want a bigger tank. A good size is 125 gallons or more. This may seem like a large tank, but it is necessary for the health of your fish. If you can't afford a large tank and the upkeep it requires, consider buying a different fish. Convict cichlids can be just as fun as oscars, but are a smaller species.
Tank setup is important. First, you'll need to find a good place for your aquarium. Keep in mind that the tanks will be extremely heavy when filled with water (larger tanks can weigh half a ton). When you set up your tank, make sure it is level. If it isn't, it could end up with cracked seals or panels.
Other than tank size, the most important issue is proper filtration. If you've never had an oscar before, you'll be surprised with how messy these fish can be. There are different ways that filters work, such as mechanical, biological, and chemical. Your filtration system should have all of these components
Mechanical filtration is made up of wool or sponge that traps large particles like food and sediment. The biological filter will be a sponge that has friendly bacteria that changes feed waste into nitrate. The chemical filtration is usually charcoal and helps remove medication and odor.
A filter that is outside the tank, preferably a canister or overflow system with a power head is the best for an oscar fish tank. Even though your filter will keep your tank clean, you'll still need to change about a quarter of the water every week to keep your fish healthy and happy.
Another thing you'll have to buy for your fish tank is a heater. The ideal temperature for an oscar is 77 degrees Faranheit. You'll want to check the temperature daily to make sure the heater doesn't break or malfunction.
Having a properly cared for fish tank is the number one thing you can do to ensure your oscar's health.
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Thought I would put this write up on Oscars
(Follow up to Rich's post in Plec's)
as when I got mine he was 3 inch and growing a inch a month
he is now nearly 8 inch .... and 3 tanks later starting off in a 3ft ;O(
pic below is not my Oscar.it is just to show you the size your little fish may reach.
Mon Mar 30, 2009 4:18 am
and good post... is this monster fish day? 
Very sad.
