Norwegian	Dane	Brit	German	Swede
water	tea	milk	coffee	beer
Dunhill	Blend	Pall Mal	Prince	Blue Master
cats	horses	birds	FISH	dogs

There are only two unambiguous facts given. The rest are  about relations. From the clues, the German is the only one remaining without a pet specified. Therefore he must be the one who owns the fish.
 

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