The Poppelsdorf castle has one more attraction: GA reader Peter Sauer has discovered an orange Koi carp in the water, which has recently started to swim around between the pond plants. This is no surprise for the University of Bonn. "In the Botanical Gardens of the University of Bonn and at the Poppelsdorfer Weiher, all kinds of creatures cavort above and below the surface of the water that actually don't belong there," says spokesman Andreas Archut.

Because time and again, people put their no longer wanted pets out there. "This is not only mean to the animals and bad for the local ecosystems, but also punishable by law." Whoever is caught doing so must expect to be charged and severely fined.

The chances of survival for the koi carp are not bad: It has enough food and space in the pond. "However, we are not able to estimate the extent to which any predators will reduce its life expectancy without further studies," explains Archut.