Does anyone here have fancy guppies?

I foolishly bought a male and female fancy guppy for my small water garden
to keep down the mosquitoes. I now have to winter them over (well actually
winter over Mom and two offspring) and I don't have a clue when I should
bring them in, if they have to have filtered water or I can simply change
the water on a daily basis (I'm going to have a very small tank by the
kitchen sink), etc. They don't eat any of the food I give them that I can
see so I don't even know about feeding them. Any help would be
appreciated... DKat