Just a quickie as this is not much to do about ferrets,
 
The rat will chew your books (I too speak from experience).  If you want to
keep your rat in an aquarium - as I do - make a tight fitting lid from good
quality wire mesh (1cm square).  I generally leave this lid off during the
day as our rats enjoy coming out (they have acces to a couple of shelves
with toys etc), and put it on at night or when we are out.
 
Paul Webster.
[Posted in FML issue 1615]