Hi Loopy, Sorry to hear about your losses, anything I can help you replace, just ask.
On a preventative note, this does bring to mind "what could be done to prevent something so simple from happening again, or to anyone else..."
Got me thinking and a little looking through some old notes and books I haven't read in a long while to find a solution... (Was a computer tech years ago when things were actually expensive enough to warrant fixing them rather than throwing them away). I found two...
1. A simple inductive load monitor that clips onto a power cord, if no current flows in the cord for a pre-set time (say 5 mins) an alarm will sound... powered by a 3v lithium cell this thing would run for 5-7 years without battery replacement. Simple but potentially disaster saving.
2. A slightly less simple High Low temperature monitor on each tank. Would have a pre-set range that if exceeded either high or low temp would sound an alarm.. Could also incorporate a high temp cut-off that would fit between the power and the heater so a stuck on heater would be switched off if it went over temp... (and back on once the tank had returned below the max temp set). Effectively eliminating finding boiled fish on your return home from work.
I would expect option one to cost about $10-15 to make, and option 2 a bit more, about $20-25.
Would anyone be interested in such devices if I was to make some, I know I will be making these for myself and installing them in my fish room.
Cheers
Wayne