Hi, I have a 125 gallon tank with an Oscar in it which I keep at 77F. On the way out the house I noticed my oscar acting a bit strange so i checked the thermometers in the tank and saw that it had jumped up to 83F I immediatly shut the heater off. What had happened was my heater controller had fallen behind the tank pulling the thermometer for the heater out of the water which caused the heater to jump a lot. I am letting the heater re calibrate to the water temp now. Safe to say I need to secure the temp controller better to avoid this and I will also be purchasing an Ink Bird controll unit to stop this from happening again.