Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Didn't work for me

This did not work for me. Tried using it in a stone bird bath of approx 15" diameter x 3/4" deep. I thought my bird bath could be described as shallow, as in the write up for the product, but the best it did was keep a thin film of water between the heater and the ice. It completely failed to keep the birdbath free of ice. Admittedly the CT winter can get cold but this heater was totally inadequate for my application.