^ That's not memory either, that's just primitive association.
I like this list, Bombularina, a lot of people also fall for the one Luimeril posted as well.
In my experience the most common ones I hear are the "only grow to tank size" "He's lonely" ones from my parents XD
EDIT: OH, my parents also think for some reason that once you fill up an aquarium, you have to keep water in it or else the sealant won't work effectively anymore. I didn't know they thought that until recently, no wonder why I was never allowed to purchase/obtain used tanks -_-