not saying i may or ever will get a big enough tank, but could a oscar live cofertably in a 30 gallon, i am think of getting one with 3 filters, lol stupid ain't it?
in my opinion an oscar can live in any size tank, obviously depending on the O's size. I think a 30 gallon would be big enough for long enough for you to save to Upgrade to a 55
A 75 is prefferable for keeping oscars, a 55 lacks the width and height that tall/wide bodied fish like oscars need. Unless you already have the larger tank for the oscar and are just growing the fish out in a smaller tank then dont do it, oscars grow very quick and will probbaly outgrow a 30 before you can upgrade.
Don't put an Oscar in a 30 gallon tank, unless you are absolutely 100% certain you will be able to purchase a larger tank down the road, in the not very distant future. They grow very quickly, they are messy, and while an adult Oscar in a bare 30 gallon tank is technically possible, it is not right.