Hello, i have and old 120 gallon tank i got up and running last week, yesterday i went to the store to purchase the fish, i got myself 3 blood parrots, two of them 3 inch the other 4 inch, along with a 2.5 inch red devil/midas, also there was a special on jack dempsey so i picked one up to see how itd work its 3inches. will there be a problem with the fish getting along?