Kronberg has no space for a third hippo,( and teh hippo exhibit there is a Desaster) and "Petra"is the mother of"Max". And waiting until"Tana"has passed away isn't a good Option-she's doing well for her Age of 54 years and could live a few more years.Hannover and Cologne could take Petra, they have space enough for one more hippo, and both places are not interested in breeding them.
I ask me, whatfor people bring Tennis balls in a zoo....maybe bag controls like some places in the usa could be also an Option for european Zoos.Or Airport Scanners...