I’ve seen this puzzle in a few places under a few names, and thought I’d have a go at solving it.
Read on to see the short solution (to the question of who owns the fish) and the full solution (of exactly who lives in which house, with their individual pets, drinks and cigars). Have a go at solving the puzzle yourself first. I worked it out simply by following the clues given, with the assumption that the clue stating ‘the green house is on the left of the white house’ meant that it was on the immediate left as so;
My solution is that the German owns the fish.
My full solution is as follows:
Or to see that in grid layout (which is how I solved it):