there is a dorado at my local aquarium store he is about 6in, the staff there said they wouldn't recommend putting anything in with one, I have seen him eat 2X now and he ate about 5 feeder fish in about 10seconds-
but these fish may be compatible large ( CATFISH, PLECOS, GAR,vampire tetra / PAYARA or maybe clown knife
but the dorado get huge, there very fast feeders, pick tank mates that will grow bigger than it and be cautious!