Tank divided oscars

Hi,

I recently introduced a new oscar into my tank which already had an
oscar in it. As you can imagine, the old oscar didn't appreciate this.
Turns out for the first time in years I overfed a fish and the new
oscar got sick - it is now on the road to recovery.

My question is, when I introduce the new oscar back into the large
tank, I want to use a tank divider. If I use a clear tank divider with
holes so the oscars can still see each other, will they gradually
acclimatise to being around each other and if I have a male female
pair, pair off when the divider is removed? Or once a divider is in,
will it have to stay there until I get a new tank? Has anyone had
experience with this situation?

Thanks!