Instruct: Classify an Amazon review as either positive or negative.
Query: MINI HEATER Aquarium Heater 7.5W for Tanks up to 5 Gallons UL

This heater doesn't hold the temperature even in 2.5 gallon tank. My betta fish was always in the cold water. The temperature didn't rise even to 78F.I am very unhappy with this product. It was OK for 1 week then the heater was cold itself. I don't know why it stopped heating, maybe it broke.