Does anyone have any thoughts to share on keeping the birds water from freezing. Right now I have a heat lamp about 6 feet over the water fount, but just dropped it down to about 3 feet tonight. It's supposed to get down to 18 degrees tonight so I'm worried it still might freeze. It was 24 last night and the water froze solid. My girls were soooo thirsty when I got home from work at noon. Are the heated waterers worth the investment? Have seen negative comments about them, so am unsure if they are worth the investment.