For fish I have 1 Oscar (12"), 1 Silver Dollar9^"), 3 Kadango (5"), 1 Gibbiceps Plec (4") in a 100.
In my 90 I have 1 Oscar (13"), 1common plec (12"), 1 Pink Convict (4.5"). You have a 150 tall. With it being 6Ft long you have plenty of room.
I have a 150 wide which is 72x24x20 (Not 72x18 as yours is). I had both of my oscars in it with room to spare. The Oscars wouldn't get along so I split them into smaller tanks.
Any fast fish (i.e. Silver Dollar) or semi-aggressive fish might work but it all depends on the Oscars. Forget about plants. Oscars like to redecorate.
FWIW- The 90 is filtered by 2 Emperor 400's and the 100 is filtered by 2 AC110's.