Instruct: Classify the given Amazon review as either positive or negative.
Query: Worked great for about a year.

I purchased this in May 2010 and was very pleased with it. It heated around 100 gallons (75/gal tank and a 30/gal sump) easily. However, I noticed this summer (June 2011) that it was no longer heating the water. Not sure what the issue is, even after making adjustments to the temperature setting.I would have expected a longer life. I like to use 100 watt heaters so that they do not turn on and off often (minimizing the wear and tear), nor will they overheat the tank quickly if it malfunctions in the "on" position.