First off, this is the wrong section. It should of been posted int he oscar tank-mates section. But I'm sure an admin will move it soon. But I'll ignore that for now and get to the point-
Be wary of what kind of silver dollar you purchase. Some can reach nearly a foot in length, such as black bars while others remain a mere 2 inches. Red hooks would be a good one, as they only grow to about 6 inches. Bristlenose plecos are great, but make sure they're males, as females may be killed. You may also want to get them big, so your oscar doesn't outgrow them and eat them. I don't know much about featherfins, never kept them. But I do know they need a fairly high ph of around 7.5 or higher.
Good Luck with it,
ARTEMIS