Interesting question-I personally think that it is not one fish-all the fish I have ever had end up acting like me-chill at times and then complete psychos-heck I could buy a feeder or rasbora and they become aggressive. I hear how people have RD, Oscars, Cats, Africans all in the same tank-not me-other than Dovii Cichlids all my fish end up being pyschos just like their dad-LOL!