Einstein's Riddle

[Brian Harvey]

"Boris Popov" <no-spam-popov at bigserver.com> writes:
> The thing is that there's no fifth pet element (fish) explicitly
>defined in the puzzle.

Of course the fish is explicit in the puzzle -- it's in the question
"who owns the fish?"

This is a well-known convention among logic-puzzle fans; it's perfectly
legitimate to treat this as if there were a clue saying "someone owns
a fish."