Was in the middle of a larger than usual water change and was leaning over the tank to put some new plants in ... what's that strange smell ... hmmm, there's smoke coming from the heater, unusual ... aaarrrrggghhhh
Had taken the water below the level of the heater thus heater had gone into overdrive and was gently cooking. Could have sworn I'd turned the thing off in the summer, apparently not.
I'm guessing that's the end of it then, can't imagine it will be reliable now having got to that heat, it sizzled as I took it out of the holder and was too hot to hold through several folds of towel.
So let that be a warning to everyone else! Always turn off heaters (or, if you think they are turned off, check that they actually are ) if the water level is going to go beneath them when you do a water change
When I forget again? As if I'd do such a thing You'll be pleased to know I checked the heater in the other tank and it too was turned on so thankfully I avoided frying both of them!
The auto cut-out is a good tip, thanks, will do a bit of research. I quite fancy one of those Hydor inline heaters that go in the filter tubing, or maybe a Rena smart heater seeing as I have the Rena filters. Would quite like to have the heaters a bit less visible. Hmmmm ... fishy shopping