Tank crashes: causes, treatment and lessons to learn.

[neoh]

I've been reading all over the internet about cases of reefers tanks crashing. Normally due to equipment failure or human error. This is of course, everyone's worst nightmare.

Some things I've learned that are common causes:

heater malfunctions
long power outages
top-off malfunctions
deep sand beds purging anaerobic gases
GFI tripping
Going on prolonged vacations with inexperienced sitters
GFO overdosing
Skimmer overflowing detrius back into the tank
rocks falling/breaking the tank
neglect

some interesting ones:

anemone going into the power head
clam spawning
fan falling into tank and electrocuting everything
working with industrial cleaners at work, coming home to do in-water maintenance without washing your hands first
contaminated salt
LFS medicating the tank, bringing a fish home and dumping in LFS water

Curious about other Canreefers, have you experienced a tank crash? What was the cause, what was the outcome, what did you do, and what could you have done differently to prevent it?