This week I visited Shinagawa Aquarium with my son. Its admission fee was 1350 yen ($10.98 €9.93) for adults, 600 yen for students. In August many visitors come to the aquarium. From August 12 to August 16 the aquarium opens at 9:30. It is 30 minutes earlier than usual. We arrived at 9:40. But many visitors have already come and the aquarium was crowded.
Here is the leaflet of the aquarium.