Green Sunfish has a large mouth(reaching to or past their eye) wavy blue lines near the mouth, adults have a black spot on their 2nd dorsal fin and their 2nd dorsal and caudal fins will have a white or yellow edge on them. Pumpkinseeds have usually orange spots with wavy blue lines and redspot near the earflap and a smaller mouth. If your sunfish are new it will take a little while for them to acclimate. Sunfish take a little cooler water than Oscars (especially Pumpkinseeds) if you redecorate your tank (move stuff around) and have hiding places the Sunfish will end up acclimating and if its a male hold its own just fine against your Oscar (especially if its a Pumpkinseed or Green Sunfish) if the tanks big enough. How long has the Sunnie been in the tank? How big is your tank, how much tank decorations do you have and what are your temps? You could also add some dither fish if your tank is big enough.
