The Paris Tropical Aquarium is next to the Forest of Vincennes and can be reach by subway Line 8 (stop: Porte Dorée). This aquarium has been trapped in time and unfortunately has a decadent air without many tourists. However, it's good to be quiet with no crowds and if going with children I to recommend the following "triplet": Aquarium, Zoo and picnic in the park of Vincennes. It's all in the same area and to spend a quiet and different afternoon in Paris is ideal.
The Paris Zoo is an ideal place to spend a quiet afternoon strolling and relaxing away from the intensity of the city. It's also next to Bosc de Vincennes park, the roads are winding and shaded and the animals seem well cared for and can be seen easily. What caught my attention is the esplanade where the giraffes are and lots of monkeys.