The Red Devil is from Central Amercia and the Oscar from the Amazon, South Amercia.
Cichlids usually have different personality and they are pretty intelligent.
The Oscar is more of a predator that will eat any fish small enough to fit in to their mouth, but they are generally not that aggressive towards other fish thier size.
Red Devil are usually mean and aggressive even with fish their size.
All Cichlids are generally territorial and they need their space.
They will fight if space is not given and not enough hiding place.
They will pretty much eat anything and not too picky. I will feed them good Cichlid pellets and bloodworms.
Use driftwood and rocks to make them have enough hiding place and they can set thier own territory.
30g: 2 Blood Parrots
75g: 1 male Convict, 1 female Flowerhorn
125g: 1 Tiger Oscar, 1 Managunese, 1 Pleco