Posted by Rich Kovarsly, P.E., CFEI on 03/02/2010 at 21:02:32:

David,

Not sure about the scenario you are proposing, but I had a number of aquarium heater fires a number of years back. they were all the same brand heater and all failed at the same location on a printed circuit board that was part of the heater assembly. A thorough examination of the heater and all the other electrical components associated with the aquarium should provide you your answer as to what happened.

Hope this helps.

Rich Kovarsky, P.E., CFEI
Pyro-Technical Investigations