My boyfriend had a severe problem with ants in his basement suite, and he
ended up putting the ant poison in the walls, out of the reach of the
ferrets, which solved the problem.  Next time he said he'd use something
called "Fossil Dust".  It's marketed as non-toxic, and is a dust with
microscopic jagged edges that kills the ants by ripping them apart.
Effective.
 
Something to be aware of, though!!!!  Soon after the poison in the walls,
Jasper, my male, started vomitting one evening after running around,
playing.  We rushed him to the vet, who said he'd eaten something quite
toxic.  We couldn't figure out what it was, as we always keep their play
area very clean.  As best as we could determine, one of the dying ants had
crawled out of the wall to die on our floor.  Jasper, the ferret vacuum,
had eaten the poison-filled ant.  It never would have occured to us, and we
were alot more vigilant after that.
 
Good luck, and let me know what you find out and what you do!
 
Ariel, Jasper, Taz and Bit
[Posted in FML issue 2300]