Ok, ok. I've got one, just for you, reefinmike.
I had a guy come in after a massive tank crash, blaming PetCo (not my shop), for killing all of his fish with a "bad" coral beauty angel. He wanted to replace EVERYTHING all at once, so I cautioned him about adding that many fish and told him I would prefer to do a water test and see what's going on BEFORE adding that many fish. But, NOOOoooooOOOOooooo, because it had to be the sick angel that killed everything.
So, I managed to talk him down to just a couple of fish, as opposed to everything, but they all died overnight (surprise, surprise).
When he brought the water test, the specific gravity was somewhere around 1.012 to 1.014. I had to question this, trying to figure out how in the world he could have *ACCIDENTALLY* gotten that low, figuring no one in their right mind would drop their salinity that much for the whole tank.
"But the other pet store told me freshwater would keep the fish from getting sick."
.... =/