lucky to have a backup heater
 

when I got home tonight,noticed all the nems not doing well,temp dropped to 74,I have 2 heaters in the tank,this shouldn't happen.then I recalled I unpluged one of then to rearrange all the plugs and forget to put it back on,and somehow the second was not plugged good enough and it's not function.
I am so lucky,tank could have crashed 1-2 days ago.

I lost 90% of my 55 gallon to a bad heater, it's a shame we spend so much on skimmers etc and it ends up being one of the cheapest parts that nukes the tank. I have 2 fail safes now though, heater is on temp control and I have my controller to shut it off if the tank is over that temp. It also emails if the temp is above/below my set points. Silly heaters.. fool me once, shame on you, fool me twice.... NOT GOING TO HAPPEN.

Glad you caught yours in time, temperature swings can really hurt.