I have one goldfish in my water tank, "Lucky" he is at least four or five years old, may be even older (I can't remember off the top of my head) and he is tough as heck!! We have frozen him, squashed him under collapsed ice, darn near cooked him with the tank heater, our cows drank the tank almost dry (it sits at a slight angle - lucky for him!) and he just keeps growing!! He is probaby 5 or 6 inches long now. We don't feed him and his fresh water comes when we fill up the tank when it needs it - I better watch out PETA is going to come after me for fish abuse!!