Almost all corals are dead

Yep I use three plus the strip type. Some of the coral might come back. What looks dead and wilting might still be ok just watch out for the brown jelly.

 

That is horrible. you poor guy. I hope everything else is ok and makes it through. I actually have 2 therms in my tank. I have learned through cooking/baking and husband brewing beer that therms can be off.

 

I have one of these on all my tanks too. My 20G tank also has a controller on it too, if the tank gets above 78º on comes my chiller, >80º it kills the power to my heater, if it gets hotter than 82º it kills my lights, if it gets hotter than 85º, then 2 of my pumps turn off, if it gets hotter than that, I give up.

 

That is impressive

 

It's recommended to set up safety nets like that in the controller's manual. I also read many of the guys and ladies here that run controllers do the same thing. I let my tank swing 1º either way for a 2º shift, I want them to have a stable living environment.

 

very scary.... this thread made me go check my temp..

 

Sorry for your loss. We use Rena (Aquarium Pharmaceuticals RENA SmartHeater) heaters in all of our tanks. They are very accurate and even have a flashing signal that lets you know if it goes a few degrees above or below your target temp.