here are a few of mine
I had a aqua 70 on my 65g brackish, the sponge got clogged an upped the basket and since I use extenders on my hob it drained over 60% of the tank before the pump lost the power to suck up
I had a 5 side corner tank that I was led to believe was a 50g when in actual it was 35g, I saw what looked like fungus starting to show on a fin so I dosed the tank with fix as if it was a 50g needless to say most of the tank inhabitants died of o2 deprivation
My worst one thus far has been my 10ft 300g after driving 2 hrs to get it we got it set up, I did a water test on it and after 4 days it cracked a straight front to back crack, thankfully I was doing tank maintenance and noticed it and got the tank emptied without the splash down. It seems that there is a metal burr in the middle brace of the tank the proverbial pea under the stack of mattresses.