I built this a couple of years ago and love it. It's a 40 gallon trash can with sand and pea gravel. I have a pvc pipe with a 20$ pump and some bamboo leftover from a pool fence. It keeps the water circulating pulling cool water from the bottom and filters from the top. I have a couple of dozen chick's and have to and water twice a week. The coolest it got here was 5 degrees last winter and only froze up once during that cold snap. I only have around 50$ in it. I built a new coop this year and am planning on changing it to look like a horse troft to match my old west theme of my coop.