What are your thoughts.... I currently have a plastic waterer outside in the pen area (with added apple cider for worm prevention) for my girls to drink and a metal container with water inside the coop. During the winter, the plastic waterer is going to have to be put away (too large and will freeze). I will need to get a freeze protector for my waterer inside the coop. I can't decide between purchasing a base for my current metal waterer or buying another plastic waterer with a heater. Which do you prefer to use? --- metal heater base or plastic waterer with heating unit. If you use the plastic waterer with the heating unit, can you add in the apple cider still? (I know not to add it to the metal container.) THANKS!!!