Just thought I would share my winter success. After all the debate on bottom drains a while back, I put one in two summers ago. Last year I upgraded my filter tanks to three 75 gallon horse troughs to allow for more water flow. This winter we had a record breaking snow fall in December. Not liking cold weather, I have to admit that I did not check on the condition of my pond under the three feet of snow. I have not idea how long the pond was frozen completely over, but at least a month. By time I realized that with the waterfall frozen over I could lose my fish, I set out to thaw it with a tank heater, one I intended to put in before the pond froze over but didn't. Under several inches of ice and 3 ft of snow, the waterfall continued to filter the water. The first tank held one small fish that came up through the bottom drain, the third and pump tank held another, both alive. Due to the filtration, my fish were happy as clams, I didn't lose one of them. Next year I intend to get the heater going before it freezes as a safety measure. I don't want to give to much to chance. I have never regretted putting in my bottom drain, it was definitely worth the expense, effort and labor.