It almost happened to me!

[sunvalley aquarist]

I happened to put my hand in my 55 gallon Discus growout tank and thought it felt kinda warm. I looked at the thermometer and it read 90, I normally keep it at 80. The heater was set at 80. Thank God I discovered this when I did or I may have woke up to boiled fish this morning!
I don't understand why aquarium heater manufacturers don't design there heaters to turn off when they fail.

 

[Terryallen]

I agree, you would think they would do that. Goodluck with that.

 

[bigfishrcool1193]

I agree with you...

however, discus should be kept in the high 80's

 

[Illbuyourcatfish]

The heater didn't fail! The discus were cold and turned it up!

 

[DBL TAP]

You're so lucky you caught it. I cooked a school of F1 Mbuna when my heater stuck on.

 

[cypherljk]

lol "The heater didn't fail! The discus were cold and turned it up!"