Okay, don’t read any further unless you’ve already tried the puzzle. It’s a classic logic puzzle and can be solved by the standard grid-technique, like commentors suggested. I did the same thing, and I got this answer:
The German owns the fish.
Did you get that too? Here’s the thing: It’s technically not correct, according to a few sources I found. Some people say the correct answer to this problem is “there’s not enough information; the fish isn’t even mentioned in the listed facts.” I’m not sure what I think, but it gives some food for thought. Consider the following new problem and you’ll see why:
Who is the American?
(Fact 1) Winston and Paul are of two different nationalities
(Fact 2) Paul is Canadian.
What do you think? Would you say “Winston” or would you say “Winston could be anything (except Canadian) given the facts”? If you say “Winston” then you’re actually assuming a third fact: One of them is an American.
In the case of Einstein’s Puzzle, we technically need a 16th fact: One of them owns a fish.
So what do you think? Those of us who solved the puzzle in the classic logic-problem grid-solution way simply assumed that fact and got on with our lives. But what do you think? Do you think we can assume that someone owns the fish even though it’s technically not a “fact?” It’s an interesting issue–perhaps just a linguistic one. Let me know what you think.
Random Walks 
Perhaps the fact is implied from the question? Or practically, it is implied from the question, but if you define fact as only the list of presented facts, the German probably keeps llamas.
But without the question, there isn’t even a puzzle, so the question must be included in some way.
Okay, now I am reminded of TOK, though since we haven’t started the language unit yet, I don’t know what we will discuss.