In most cases aquarium type cages are better than ferret cages, as long as
they're large and well ventilated.  They keep people from sticking their
fingers into the cage when no one's looking, preventing possible health
hazards.  I don't mean fish tanks, at one PetCo I frequent, They put their
7-9 week old Marshall Farms ferrets in a 5ft.  diameter round cage.  It's
probably around 4ft.  high.  It's covered in tiny holes, giving the ferrets
plenty of air but keeping people from touching the ferrets.
 
The cage is set up right in the middle of the store, in-between the shelter
cats and dogs they foster.  They also use corn husks instead of wood
shavings, and have 2 water bottles, 1 water bowl, and 2 food bowls, though
they only have 4-5 ferrets at a time.  There are two designated "Ferret
Handlers" who are the only employees allowed to feed/water/pick up the
kits, both own there own ferrets.  They must disinfect their hands and have
anyone who's planning on touching a ferret disinfect theirs.  Anyway, my
point(s) is(are), sometimes aquariums are better, and not all pet stores
are horrible.
[Posted in FML issue 3028]