for one oscar you need about a 75gal. with good filtration...........also need to keep that tank clean with lots of water changes and vacumming the gravel......they're extremely messy fish.........
I Agree good advice ! i have two 10" oscars in a 180gal and a fluval fx5 canister filter and i do 2 water changes a week sometimes just one but thats because i like my water to be next to perfect.
A 75g is a great size for a single oscar tank,thats the size I have with one pleco.one magnum 350 and a ugf with 2 350gph powerheads for filtration works real well cause my oscar isnt much for digging