They offer military discount
If you're a member of the Seattle or King County libraries, you can reserve a day pass to the aquarium for free through your library's website! You need to do it 2-4 weeks in advance, though.
According to their website, kids 12 and under are 19.95 compared to the normal 29.95. It doesn't say anything about low income discounts, but if you get your tickets online you can save an extra $2
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