It worked great first two weeks in the pond when the temperature was hovering at 25. There was a real nice diameter of open water made by the unit. This week we were at 8 degrees the unit stopped functioning. Ice has formed on and around the unit. I have a very very small hole for gases to escape. I am concerned for my fish. The light on the heater is red indicating it is in the warming stage. It is not warm. The unit is touchable. The water is freezing. Sometimes the light is green when it should be red. I will be returning this unit. I can't say how disappointed I am. My fish are too.

Definitely a much better pond heater than my former heater units I have previously had. Definitely used less electricity.

Also for those that are not aware, it is good to continue having some water flow in the winter and it will help keep pond from freezing. But make sure that the flow does not cause any splashing as that will cause more chance of water freezing where it splashes.

Hopefully I have as much luck in the next couple of years with it. My previous heaters were lucky to make it through 2 winter seasons.

End of season 1 using this pond heater for a very small plastic lined fish pond in PA, USA. This winter was a bit milder then the last 2, and this heater worked perfectly. It has a red light when heating and a green light when it is not. We did get one major snow storm. Over 36" and this heater worked as a charm, keeping the top of the pond clear. During some freezing periods, I did get a thin layer of ice, (as expected) but it was always clear, a few inches around the floatng heater. I hope it continues to work for multiple seasons.
2017 update: this worked fine for season 2 (winter 2016/2017.)

This was the best pond heater that I have ever bought....for a month. Then it died. I called Laguna to replace it, and sat on hold for 45 minutes and finally gave up. Now I have an $80 pond heater that I will be throwing out today. Thanks Laguna for your fantastic product and customer service!!

This little gem is worth buying! We've had a 3000-gallon pond for about 5 years and for several winters, we've used stock tank heaters, which work fine while they're working, but we seemed to need to replace them every couple of years. Plus, after that extremely hard winter about 2 years ago, we discovered the hard way, the value of having 2 separate heaters plugged into 2 different outlets in case one dies/malfunctions and all the fish die as well... So we did our research on Amazon and settled on the Laguna Pond Heater.

At first, it doesn't look like very sturdy, but it has served our pond well for 2 winters. Our favorite feature has to be the little green/red light that lets us know all is working. We have had some issues with moisture tripping our GFI outlet this winter, and this light is a life-saver! We just walk by the pond from time to time to make sure it's working. And even if the ice is frozen up to the edge of the heater, the water underneath is thawed at bitter near-zero and below-zero temps.

The cord on this unit is plenty long (around 22 feet), but I do find that the heater still drifts to the edge of the pond, so if you want it more centrally located, you will need to find some way to anchor it, either with fishing string or a board across the pond, etc. The light is red when the unit is heating and it turns green when the desired temperature is reached. We have a rubber liner and have had no issues with it touching the liner, although we generally keep it floating out from the edge anyway.

Last winter we used this in combination with an aerator/bubbler, and we had a continually nice open area; this year, our bubbler died, and we still have managed to keep our pond heated, although with a bit smaller surface. However, it was adequate enough to allow for gas exchanges in our pond, to protect the the fish and plants. I do like having the combination of both in the winter and we are in the process of finding a new aerator.