You don't have to give the location, simply post pics of the pond/spring, posting pics of the pond/spring won't reveal its location if people have no idea where to look for it etc.
Either way though, this sounds completely posible to me, although depending on which fish were dumped in the pond and when and in what numbers, a lot of fish could be quite inbred (i wouldn't be suprised if the guppys were if no new ones had been added to the pond over the last year).