FACTS OF THE PUZZLE
1. There are five houses in five different colours.
2. In each house lives a person of a different nationality.
3. These five owners drink a certain beverage, smoke a certain brand of
cigarette and keep a certain pet.
4. No owners have the same pet, smoke the same brand of smoke or drink
the same drink.

HINTS
1. The Brit lives in the red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the left of the white house.
5. The green house owner drinks coffee.
6. The person who smokes Pall Mall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The man living in the house right in the center drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blend lives next to the one who keeps cats.
11. The man who keeps horses lives next to the man who smokes Dunhill.
12. The owner who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The man who smokes Blend has a neighbour who drinks water.

The question is: WHO OWNS FISH?

We start by making a five by five table where each column denotes one of the five houses and the five rows denote the nationality, house color, drink, cigarette, and pet.   We can start to fill in this table with the information in clues 8 and 9.

 Norwigian milk

By clue 14, the second house is blue.  The green house/white house combination from clue 4 cannot be 1-2 or 2-3 because the second house is blue.  It also cannot be 3-4 because the green house owner drinks coffee (from clue 5) and the third house owner drinks milk. So the green house is fourth and the white house is fifth.  From clue 5, the green house owner drinks coffee.  This brings the table up to:

 Norwegian blue green white milk coffee

The red house with the Briton (from clue 1) cannot be the second, fourth or fifth house (which are blue, green, and white), nor can it be the first house (which contains a Norwegian), so it is the third house.  Therefore, the yellow house with the Dunhill smoker (from clue 7) must be the first house.  From clue 11, the horse-keeper is in the second house.  The table now looks like this:

 Norwegian Briton yellow blue red green white milk coffee Dunhill horses

What does the person in the first house drink?  Not milk or coffee, because that is the beverage of the third and fourth houses.  Not tea, because the Dane drinks tea (clue 3) and the first house contains a Norwegian.  Not beer, because the Blue Master smoker drinks beer (clue 12) and the first house owner smokes Dunhill.  Therefore, the first house owner must be the water drinker mentioned in clue 15, so the Blend smoker is in the second house.  This Blend smoker cannot drink beer (again, by clue 12), so the beer-drinking Blue Master-smoking person must live in the fifth house, and the tea-drinking Dane (from clue 3) lives in the second house.

 Norwegian Dane Briton yellow blue red green white water tea milk coffee beer Dunhill Blend Blue Master horses

The German who smokes Prince (clue 13) must be in the fouth house.  The Swede must live in the fifth house; by clue 2 he raises dogs.  The Pall Mall smoker lives in the third house; by clue 6 he raises birds.  The cat-raiser lives next to the Blend-smoker in the second house (by clue 10); this cannot be the third house so it must be in the first house.  Therefore, the only place for the fish-raiser to live is the fourth house.

 Norwegian Dane Briton German Swede yellow blue red green white water tea milk coffee beer Dunhill Blend Pall Mall Prince Blue Master cats horses birds fish dogs

Therefore, it is the coffee-drinking, Prince-smoking German in the green house that raises fish.