The black stuff is clarified with isinglass - a form of gelatine made from the air bladders of fish. It's only a minute amount but technically it's still a fishy pint.

A vegetarian-friendly alternative used in some beers is Irish moss. All German beers are also safe for veggies because of a law from 1516 which states their beer must contain only four products - hops, water, sugar and yeast.