I've had a minor problem this year with my tank water being a bit on the warm side. I panicked this morning when I came home from work to find my water temperature was 91*!! 
QUICK WITH THE ICE!!! 
After putting about a gallon of ice cubes in the tank to cool it down
I start getting suspicious. How the heck is the water that hot? Doesn't feel hot; none of the peripherals feel hot... 
so I grab the digital thermometer sensor & hold it in my fist for a minute... it's a brand new thermometer, darn thing should work. Sure enough, I have a body temperature of 120* I always knew I was a hot guy but that's just 
right there.
Turns out, the little sensor was never sealed properly. Water got into the sensor making it read stoopid. Went to the store & bought a different one today.
Glad I didn't hurt any of my fish.
QUICK WITH THE ICE!!! After putting about a gallon of ice cubes in the tank to cool it down
I start getting suspicious. How the heck is the water that hot? Doesn't feel hot; none of the peripherals feel hot... so I grab the digital thermometer sensor & hold it in my fist for a minute... it's a brand new thermometer, darn thing should work. Sure enough, I have a body temperature of 120* I always knew I was a hot guy but that's just right there.Turns out, the little sensor was never sealed properly. Water got into the sensor making it read stoopid. Went to the store & bought a different one today.
Glad I didn't hurt any of my fish.
ill test my thermometer when i buy it. glad too head you didn't murder your fish? you might want too keep a close eye on them? the ice could have cooled down the water rapidly and it could have hurt the fish