Of course sanitizing a tank is futile ;-). My statement was due to 2 reasons:With a background in microbiology, you must appreciate how futile sanitizing is - everything you try to remove from the tank comes right back again. And speaking of which - there were no signs of disease.... So what exactly are you "cleaning" other than the beneficial bacteria, which keep the fish safe. No where else in the fish keeping world does anyone consider starting over when a fish dies. It's just such a counterproductive practice.