Thinking about adding an Eye biter and Livingstone in the oscar tank. All are large size (Cichlids - 6-7 inch) and oscar around 10-11 inch. Do it? don't ? Tank size 150.
I would say no because they come from much different water types, so there are going to be problems there. Oscars need soft acidic water while the livingstonii and eyebiter needs harder basic water. Temperament wise there is also going to be a lot of aggression.
Different continents, with different modes of communication of aggression and backing down, leading to more fights, especially if they are within 25% of each other's mass. I'm assuming you have hard water.