The best flea killer we have found for ferrets is ADVANTAGE for cats,
You only use two drops on each ferret.  It has been found to be safe and
effective in getting rid of fleas.  It has been reccommended by all three
of our vets.  We live in Florida and deal with fleas year round, and have
used ADVANTAGE for over a year now with no side effects except flea free
animals.  I would strongly suggest using this product on any animal with
flea problems.  Just be sure and use the CAT ADVANTAGE and only two or
three drops.  They only have to be treated once a month, but I only use it
when I see fleas.  I used it three months ago and have had no fleas since.
It really works, at least for all the ferrets here at Widget's Halfway
House.  Any rescue is immediately checked for fleas upon arrivial and
treated before allowed near the main group.  Ofcourse all newcomers are
seperated for two weeks anyway.  Just my thoughts on flea control.
[Posted in FML issue 2476]