Just thought I would post my $0.02 on the subject.
 
We bought our 4 story bubble cage for $50 when they were being
discontinuted from Petco.  (There had been a problem with a too large of
an opening at the top of the cage and ferrets could get out/caught in the
hole.  We found this out later but our ferrets have always been to big to
get through the hole, so no problems there).  We bought the cage about a
month or two even before we had ferrets since we were trying to save up the
money.  Instead, we put a stuffed ferret (Rocket the ferret) inside of it
and made a game out of moving the poor thing around the cage every day
(yes, we were pathetic).
 
Once we finally got our 2 ferrets, they would have nothing to do with the
tubes at first.  They didn't even like the ramps!  They would only use the
first ramp to get up to their food and back down to the litter pan.  We
started making them use the ramps by putting them in their hammock
(attached to the top of the cage) so if they wanted down, they had to
manuever through something.  Took them a while to realize the hole on the
opposite top level shelf meant "oops i'm gonna fall to the bottom" Once
they understood that, they started using the ramp ..  until it broke.  (My
boyfriend had broke one tab at the beginning, the ferrets broke the other
one).  To fix the problem, I moved the shelf that was under their hammock
to make a stairway up to the top shelf.
 
As for using the tubes that run around the outside of the cage, it took
them a good month to start to use them.  Our bigger ferret would only climb
up in there if we would tease him with raisins and then would look lost
once he got up in there.  Then one day, I had put them in the cage before
they were done playing so I could clean.  Next thing I know, I hear this
awful racket and I think they are doing something to each other.  Look at
the cage and they are both merrily climbing through the tubes.  Nowadays,
the outside tubes are used to dry off in ("mom, how *could* you give us a
bath!") and as our little ones personal attack zone ("i am the king of the
bubble tubes!  no one may enter without a bite on the nose.")  The inside
tube is used as an escape hatch.  ("i'm on the top shelf and mom is opening
the door.  wheeeee, here i come to try to get out")
 
Oh, and I know all about them not being able to get into the cage while up
on those rolling casters.  I had one almost hang himself on his collar
trying to get into it while I was cleaning parts of it.  For a long time,
we would put a cardboard box in front of it so they could jump onto the box
and then into the cage.  Only problem with that was it was a computer paper
box and they just loved to open up the top and play inside.  Once the top
was open, it had to be closed before they could get back inside of the
cage.  Now they have a ramp leading up to the cage.  It's a 12 step bird
ladder which we covered in carpet and stapled/zipped stripped tight.  It
hooks to the middle of the cage door and they can easily run up and down
it.  It also gives them a new play toy to scratch at.
 
Rowan
[Posted in FML issue 2941]