I was going to try a MiraFount but after reading this I bought another Ritchie - - - But I modify mine.  I bought a piece of 3" thick styrofoam insulation and lined the fountain with it.  Yes I know it comes with 1" but I don't like high electricity bills.

Also when I put them in I get 3 five gallon buckets with the lids still on and drill a 1 & 1/2 inch hole in the middle of the top and bottom of each then drill three more holes around the edge of the ends as well ( total of 4 holes in each top and bottom) and run the pipe thru the middle up to the top of the concrete under the fountain.  This allows ground heat to come up into the fountain and keeps the pipe from coming into contact with the cold ground.  Also be liberal with the caulking to stop drafts under the fountain - - - unless you are much better than me the fountain will not have an air tight seal the the concrete.

I also use a theromator and adjust the thermastat to keep the water at 40 degrees.  This normally takes me about three days to get right but never needs setting again after that. That is plenty warm enough and does not waste power.

If I close off one half I also float a piece of insulation on the side I'm not using befor I close the lid.  With these easy and cheap modifications I have very good luck and so I don't think I will try the MiraFount.