"Describing the nitrogen cycle is a one in ear out the other sort of thing i notice when talking to customers. "Its that non-existent thing that the fish nerd is telling me about for some reason."
At this point, i describe it in a dumbed down version that pretty much says the tank has to "establish" itself." --- Exactly!!
At the end of my rope I end up saying " Well add fish now and you'll be buying more in a weeks time when these die!" Not quite so bluntly but along those lines... Bless our poor fishy friends.