A friend of mine had a similar problem.  She suggests diverting the ferrets
attention when the undesirable behavior gets too aggressive.  The ferrets
slept in different cages for a while.  She recomends that you should NOT
seperate them during play however since the ferrets are just testing one
another.  Sometimes a ferrets' play seems more aggresive than it really is.
 
My friend's ferrets (Kelsey 3yr and Quincy 9weeks) are sleeping togather by
thier own will.  They seem to get along fine.  I took my spastic 12week old
to visit the other day.  When my Claudia started to punk Quincy, his "big
sister" took up for him.  This showed us that even though Kelsey and Quincy
fought to begin with, they are good friends now.
 
Hope this helps
Britta
[Posted in FML issue 1560]