The aquarium was bought for $120 x 50/100 = $<<120*50/100=60>>60 less.
So the marked down price of the aquarium was $120 - $60 = $<<120-60=60>>60.
Axel paid $60 x 5/100 = $<<60*5/100=3>>3 additional for the sales tax.
Therefore, the total cost of the aquarium was $60 + $3 = $<<60+3=63>>63.
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