Great suggestions Connie. Rich, when they are first together in that clean tub, and you've given them a bit of a wash so they don't have a "community" smell that's different - put in a favored treat and enough of it they don't need to fight over it. Anything from your fridge will do - pizza crust, whatever. Then just keep listening in. When I hear any rat fight break out, I run in, give the enclosure a smack and holler "BAD RAT!!!" (yes it's quite the sight LMAO). Any rats that are having a scuffle always break it up, race to a corner and cuddle each other because apparently I'm the meanest rat in the house.