robyn,

can i breed non fancy guppies for tollerance of freezing water - why hasnt this been done - i think that this would be feasable under restrictive conditions

Many people tell me stories about their fish and ponds. No one has ever told me their guppies survived overwintering in a zone that has a real winter. As far as I know, they don't survive ever below about 50 degrees F. I put some outside in a tub pond one spring, too early. The water was maybe 55 degrees F. They died over a few days. Even the most hardy guppies should not be kept below 60 degrees F if it can be helped. I suppose if you slowly lowered the temperature, and then saved those guppies to breed in the summer, you might over time, be able to get a strain that can take lower temperatures but I highly doubt down to freezing. I would bet others have tried. Common guppies look so much like mosquito fish that if you like a fish like that that can live down to freezing, the mosquito fish will have to do.