Air pump w/stone and stock tank heater on the standby when temps go
too low. Or, a small pump on shelf moving water at the surface. ~ jan

Sorry that I'm so dense Jan, but could you explain this more? I'm new to
ponds and I'm not sure quite what you're describing. Thanks ---Steve

Go to your local pet shop or Walmart type store and check out the aquarium
section, it will make more sense. An air pump runs air thru tubing to a
diffuser causing multiple bubbling below the surface. Moving water doesn't
freeze.... course we ponders know that isn't always so, thus a stock tank
heater on standby (in the pond, not plug in) is a good back up. ~ jan