A big indoor pond is definitely going to give you the most bang for your buck. I like the idea of a window...looking at fish from above just doesn't do it for me.
In regards to my heaters, June through August I unplug them because it's so hot out here in Concord there's no need to run them at all. May and September, the heaters barely come on, but during the coldest winter months (typically December and January) they can draw up to 300KWhrs per month to maintain 78F. That translates into around $75 a month just to heat it. But it's worth it to me. Not sure if you saw that I was originally keeping goldfish...they were ok, but I really like my Wide Bar SDs, big shoal of CLs and all the others I have.
