costs of setting up a pond?

[Muller]

Agreed that 6' is over kill for your area. Mine is only 3' deep and we get down to -20 only for 1-2 weeks though. I have not had a casualty yet due to freezing. I use a de-icing ring when it starts freezing over just to keep an open hole in the ice for gas exchange. I also use a Laguna pump with the submersible filter and am very happy with both.
PUMP
http://www.lagunaponds.com/en_us/lag...fall-pump-kit/
FILTER
http://www.lagunaponds.com/en_us/lag...-filter-pt505/

Live plants greatly help with filtering the water and adding some food for the koi. I have never had to suck out the bottom or do a water change on my pond with my setup. The only losses I have had is from raccoons which I have dealt with.
Good luck and enjoy your pond.