Review on HiTauing Aquarium Heater - Upgraded 300W/500W Fish Tank Heater with Intelligent Water Level Detection, Auto-Shutoff, and Advanced Temperature Control System - Ideal for Saltwater and Freshwater Tanks by Andrea Webb

This does exactly what they say. Really accurate and keeps the temperature very well. The digital reader is excellent. The previous heater I had was analog and of course it failed and I didn't realize it was no longer holding the temperature. The heater was still on, but the water was freezing. The only thing I would change is the way you hang it on the tank. Maybe it should have a strong suction cup or some way to attach it to the glass of the tank. At the moment it just hangs there and can swing back and forth.