It sucks when perfectly seemingly fine fish die for no reason. In my tank, my little racoon butterfly was fine one day, eating just great and looked normal and the next day when I got home from work, it was stuck nearly dead on the Koralia. It died shortly after... no evidence of any injuries or anything. It had been in the tank for a couple of months.

Then in the big tank, one of Kristy's little anthias died for no reason. It has been in the tank 6+ months. When we pulled it out, it was in perfect shape. No sign of any injuries or anything picking on it.

When fish go suicidal and go carpet surfing, it sucks, but not as bad as when they die for no reason. :(