Assuming one has a large tank say 500 + gallons. What type of aro tends to be easier to keep in a group? This would include the Asain varieties, but I am particulary interested between the silver and black( i soo much prefer the physical look of these, the black being my favorite of all). Also what is the best number to have? Do the silvers and black view each other as the same? example would 2 blacks and 3 silvers be a problem? Or would this result in the two blacks fighting and show no aggersion to the silvers? I am trying to write down my dream list and this info is crucial to me. Thanks for your help, aro's are def. must have in the list.