Did u unplug heater for waterchange? If not it got too hot and thats what broke it. Higher wattage heats faster so it wont be on as much. Make sure to always unplug heater when u take out water. As long as water temp stays above 70° F ur fish will be fine.
Sent from my SPH-L720 using Aquarium Advice mobile app
\m/ (>_<) \m/