Doesn't look like a fire-bellied newt to me, I would say this is one of the paddle-tailed newts [Pachytriton labiatus perhaps?]
I visited Rhenen last week, and in the aquarium-building, there was only one salamander and it was labeled as fire-bellied newt. It was a bit hidden from sight, but it did have the orange belly markings. It does look like a Pachytriton though, I guess Rhenen just needs to update their signage.
Could be the case, they seem to often be mislabeled. We have a Pachytriton sp. that was advertised as a fire-bellied newt in the aquatics shop. Certainly knew it wasn't H. orientalis because we keep them as well, and the Pachytriton is about 3x the size
