I had a bit of a horrible experience a couple of nights ago with a heater exploding and demolishing a tank.
The tank had been dry for a couple of weeks, everything was unplugged.
I removed everything from the tank and gave it a good clean, including the heater then used the heater to keep the fry warm in a 5 Gal salt bucket whilst I added water to the tank.
Once it was ready I unplugged the heater, put it into the tank, added the fry to the kressel in the tank and then turned the heater on.
Initially the light came on, on the heater and then flickered. Then it looked like is started to ark.
I turned off the power to the heater, as I did so the ark got really bright and then the heater exploded.
The tank is 6mm glass and two large holes were punched through it.
I have to say, this was one of the scariest things I have had happen. Massive bang, water everywhere, nasty smell and the power shutting off to the sound of water poring out of the tank.
The remains of the offending heater (ironically the brand is listed on one of the shattered pieces, so Im not sure what it was. I do have another one somewhere so thats getting removed).
Whats left of the tank and my kressle
A few days later the fry are still alive now back in the 5gal salt bucket with another heater, I was expecting them to be dead, but it looks like I should keep feeding them and put them back into another tank.