If you want to see really good german zoos, visit the smaller zoos, tehy are much betetr than the big ones ! The smaller zoos are building better exhibits with less money than the big zoos, and most of the small zoso have species in their collections, whcih can be seen very seldom in captivty.
Forget Hannover, that's a Disney Zoo, the animals are not important in that zoos and the exhibits are mostly very bad, altough they are new. This zoo wants to make a lot of money and is not doing not very much in conservation.
Leipzig is much betetr, they have a better information sytem for the visitor, the exhibits are much better, and of course, the collection is much better than Hannover. And the Zoo is involved in diffrent conservation prorgamms, especially in vietnam.
Cologne was once a very good zoo, until they have build this horrible elephant house. Unfortunately, they have now a few just indoor exhibits for some monekeys(Gibbons ! )or tree kangaroos, very poor for a big german zoo. MOst german zoos are now only interested in breeding elephants, whats very important for the highly endangered african elephant ! The only reason why they are all now breeding elephants is to make money, and this no secret.
Duisburg is indeed now a good zoo, especially they have gave up keeping beluga whales and commerson dolphins.
Forget Hagenbeck ! A famous Name is the only thing this park can offer, but the exhibits behind this name are so poor. Its allowed to the visitors, to feed the animals. The elephants are standing the whole day at the exhibits edge to get food from the visitors, guarde by the keepers. If one elephant tries to leave his place, immediatly a keepers end him back, using the elephant hook...Oh yes, a very good elephant keeping is that...
The lion exhibit is a dsaster, the lion inside cages are a desaster also, and the new Tropical Aquarium is poor and bad for the animals, so the inbddor exhibit for ringtailed lemurs. But its important, its good looking for the vistors.. Ring taile dlemurs loves the sunlight and sun bathes, but this is not possible for the Hagenbeck Lemurs, poor guys....
I don't like this zoo, its one of the worst zoos in germany.
But let me tell you, there is no Best Zoo in germany. Every Zoo has his good and bad parts, but my own experience is, the smaller zoos asl ike as Nordhorn,Thüle or Rheine, are much better than the big zoos.