We often get that in the shop I work at.
When some of the dwarfs have been fighting we split them up and put them in separate cages, but every time anyone goes near the tank they squeak as if they thing any advance is a threat. Especially with the really bullied ones, like they've been really shaken up. Poor babies.
Normally it just take a few days of peace and quiet to let them settle down, then we start doing some short handling practice to warm them up to people.