i should have added: defective equipment at no fault of the hobbyist. Although not very common, there are incidents of heater or pump breaking and killing or “ crashing” the tank. luckily, i’ve not had either happen and haven’t had any type of crash in my 15 years of reefkeeping (knock on wood). That’s not to say i’m special or doing anything unique. i just follow what others have done before me and read lots of books and stuff. and try to apply it conscientiously.From what I saw working in LFS the common causes are: over feeding, over stocking, not monitoring water parameters, user error with equipment, accidents involving some sort of chemical getting into the water (kids dumping detergent etc.). A lot of time when people say “oh, my tank crashed “ I just don’t believe them. What is more likely is that they just totally neglected the tank and everything died. If you want to call gross neglect a “crash” I suppose that works too.