one time i put some live rock in my sump and accidentally crushed a glass heater underneath.
later when evening came and the temp dropped, the heater came on. i was sitting about 20 feet from the sump at the time, and all of the sudden i saw what looked like someone arc welding under water in my sump. it went on for about 5 seconds before i jumped up and pulled the plug.
the GFCI didn't even trip.
the weirdest thing was that nothing died. all the sps
browned out, but later colored back up, and the xenia turned as white as paper for about a month. nothing else was effected.
sorry about your dead looking livestock. what do you consider "dead looking" btw? maybe they are just a little freaked out.