Holiday tension: How do you deal with conflict in your tank?

[FinnG]

The longer I'm into this hobby, the harder it is to decide which fish I want to add to the aquarium. I want Acanthurus leucosternon-but there are already adult Acanthurus sohal and Paracanthurus Hepatus, and it will be an epic battle. I want butterfly fish-but my Chelmon rostratus will not accept it, and there will be a battle. I want some Angelfish-but they are not reefsafe, and I understand that I was lucky with mine. Therefore, recently new residents-at most some Valenciennea helsdingenii or similar.