The New England Aquarium has announced a new timed ticketing system. Here’s their FAQ relating to using a library pass…
I have a library pass. How do I get a timed ticket?
If you have a library pass, you will be able to purchase a discounted timed ticket at General Admission windows.
Can I use my complimentary Aquarium pass or library pass to purchase tickets online?
Passes and discounts like the library pass cannot be used for online ticket purchases. The best way to ensure that you get the time you want is to arrive with your passes early in the day and head to the Aquarium Box Office.