I'll post an update later this winter, but we just got this new stock tank de-icer. It seemed to be the best deal I could find online, plus we have Amazon Prime.
It got down to 12F last week (before I got the stock tank de-icer), which is quite cold for November here. Occasionally it will get below 0F here. Thin layer of ice on top and frozen nipples in our 3 gallon bucket setup. By the time I put the de-icer in the bucket, it was up to 18F. It took a full 24+ hours for the de-icer to melt the ice in the nipples, even though the heating element is only a few inches from the nipples. The ice on top of the water was melted in less than 10 hours. The chart for this brand says the 250W version is good for up to a 30 gallon stock tank in my temp zone. I think it will be fine, because I think it is meant to KEEP ice from forming, rather than melting ice already there (and below the heat element, since heat rises). It's been good since that time, though the coldest it's been since than has been 21F and it has not been above freezing for nearly two weeks now.
http://www.amazon.com/Ultimate-All-...F8&qid=1385510423&sr=8-2&keywords=k&h+de-icer
Note that the link is for the 500W version, click on the 250W button on the product page for the less expensive 250W version.
It got down to 12F last week (before I got the stock tank de-icer), which is quite cold for November here. Occasionally it will get below 0F here. Thin layer of ice on top and frozen nipples in our 3 gallon bucket setup. By the time I put the de-icer in the bucket, it was up to 18F. It took a full 24+ hours for the de-icer to melt the ice in the nipples, even though the heating element is only a few inches from the nipples. The ice on top of the water was melted in less than 10 hours. The chart for this brand says the 250W version is good for up to a 30 gallon stock tank in my temp zone. I think it will be fine, because I think it is meant to KEEP ice from forming, rather than melting ice already there (and below the heat element, since heat rises). It's been good since that time, though the coldest it's been since than has been 21F and it has not been above freezing for nearly two weeks now.
http://www.amazon.com/Ultimate-All-...F8&qid=1385510423&sr=8-2&keywords=k&h+de-icer
Note that the link is for the 500W version, click on the 250W button on the product page for the less expensive 250W version.