Review on 🐠 Aqueon Submersible Aquarium Heater: Optimal Temperature Control for Vibrant Fish Health by Jennifer Kiel

It's May 2021 now so it's been running for 2.5 years. I use a glass thermometer to make sure the temperature stays within an acceptable range and my hands are in the water at least once or twice a week to clean the glass, trim plants, or do other aquarium maintenance, so when the water gets too hot is or too cold, I would have caught him. I can't speak for the water temperature being constant, but water temperature is not inherently constant and slight fluctuations don't seem to bother my fish and neither do I.