Note:

The suggested steps to the final answer below are not unique and are just one of several logical approaches.

First consider color.
The Norwegian lives in the first house (fact 9)
Which is next to the blue house (fact 14).
Thus, the second house is blue.
The green house is to the left of the white house (fact 4)
Which means that the green house must be either the third or fourth house.
But the green house cannot be the third (center) house,
Because the owner of the center house drinks milk (fact 8)
And the owner of the green house drinks coffee (fact 5).
Thus, the fourth house is green and the fifth house is white.
Since the Norwegian lives in the first house (fact 9),
And the Brit. lives in the red house (fact 1),
The first house must be yellow, leaving the middle house red.
Next consider drinks.
The owner of the red (third) house is a Brit. (fact 1) who drinks milk (fact 8)
The owner of the green (fourth) house drinks coffee (fact 5).
The Norwegian lives in the yellow (first) house.
The Dane drinks tea (fact 3),
And must be the owner of either the blue or white house.
But he can’t be the owner of the white house.
If he were, then the beer-drinking Bluemaster smoker (fact 12)
Would have to live in the blue house,
Making the Norwegian in the yellow house drink water.
But that can’t be right because………..
The water drinker lives next to the owner who smokes Blends, not Bluemaster.
Thus, the Dane must live in the blue house,
And since the beer-drinking, Bluemasters smoker
Cannot live in the yellow house
He must live in the white house,
Leaving the Norwegian in the yellow house drinking water.
Next consider nationality.
Only the German and Swede are unaccounted for.
The German smokes Prince (fact 13)
And thus must live in the green house,
Since the owner of the white house smokes Bluemaster.
Thus, the Swede must live in the white house.
What about cigars?
Only Blends and Pall Mall are unaccounted for.
The Pall Mall smoker rears birds (fact 6)
And thus cannot live in the blue house, which has horses.
Thus, the Pall Mall smoker lives in the red house
And the Blends smoker in the blue house.
Finally, what about pets?
The horse and bird owners have been identified.
The Swede keeps dogs as pets (fact 2),
Which means dogs are pets in the white house.
The Blends smoker lives next to the cat owner,
Which indicates that cats are the pet in the yellow house.

And finally, the only pet left

(Although it is not even mentioned explicitly in the puzzle)

Is fish, which are the pets of the coffee-drinking,
Prince-smoking German living in the green house.

So there you have it - The German owns the fish.