Instruct: Classify the given Amazon review as either positive or negative.
Query: Doesn't heat up the water enough?

I got this as a gift for my GF's Betta that is in a 5gallon tank. The thermometer never passes 75, even when the temperature is turned up to the max of 88 degrees. I'll let another week by and update. I gave it 2 stars because it does heat up the tank, from 60 to 75, but it doesn't heat up to the correct degrees on the dial.