Adult $49.95 Child $29.95 (Ages 3-12, under 3 free) http://www.montereybayaquarium.org/visit/admission-tickets
I just went yesterday and expected to pay $100 since there were 2 of us (adults) but was charged $75 .... I don't know if there was some difference for paying together versus separately but a pleasant surprise.
The Aquarium is only free for residents of Monterey, Santa Cruz and San Benito counties. Only till the 9th of December.
The aquarium is free right now. Adults just need their ID.
I think adult admission is $50 but I don't know how much it is for a child.
Thanks! Your answer is awaiting moderation.