I think the aro and dats should be ok. Most fish leave dats alone because of the body shape and dorsal spikes. I understand if you cannot part with the oscars but please seperate them to their own tank. Oscars are very suceptable to disease and the dats and aro will catch it next. Also what are you feeding your fish? If your fish are eating plletized food you may want to purchase dats that are trained to eat non live foods or seperate them until you can train them yourself. This way you wont have to feed live and compromise your current fishes diet
I put my 4.5 inch IT in with my 17 inch rtg and they are fine,infact unbelievably the dat kept nipping the aros fins as he swam past.lol!
He doesnt do this anymore.must have had a slap or something but the dat follows the aro round like his shadow and his best buddy!
Id definitely not mix with oscars though!