IMHO I would recommend if you're just going to keep one oscar, why don't you put it in a 75/90 or 125 gallon tank. Just that they are cheaper and more common out there. 180 would be fine for a small community of cichlids with the oscar being the centerpiece and smaller s/a cichlids like a festivums, severums along with some of the larger tetras / dither fish that are too large to become a snack.