Here's what I plan to do this winter (ok, it's really never winter here.
).
I'm going to maintain the water level. Since it only gets below freezing a couple days a year and then only for a few hours at a time in the early hours of the morning I'm going to leave the pump on the timer and it's set to run from 3:00am till 7:00am. That way it'll be circulating and preventing anything from freezing during the freezing hours.
My fountain has been ran this way for the last 5 years and I'ts never hurt anything, though at times it looks like an ice cake.

I'm going to maintain the water level. Since it only gets below freezing a couple days a year and then only for a few hours at a time in the early hours of the morning I'm going to leave the pump on the timer and it's set to run from 3:00am till 7:00am. That way it'll be circulating and preventing anything from freezing during the freezing hours.
My fountain has been ran this way for the last 5 years and I'ts never hurt anything, though at times it looks like an ice cake.