The album debuted at number one in Denmark and Norway while peaking inside the top ten in seven countries. It sold 39,000 copies in its first week in Denmark, becoming the fastest-selling album of the decade. The album became the second best-selling album of 2000, selling 174,523 copies. As of August 2001, Aquarius had sold 265,000 copies in Denmark. It became the third best selling album of the 2000s in Denmark.
In the United States, the album debuted at number 82 on the Billboard 200 and spent six weeks on the chart. This is a significant drop from their last album Aquarium (1997), which peaked at number seven and spent 50 weeks on the chart. Aquarius has been certified platinum by the International Federation of the Phonographic Industry (IFPI) for shipments of one million copies inside Europe. Worldwide, the album has sold four million copies.
The lead single, "Cartoon Heroes", peaked at number one in Denmark and Norway, reached number 7 in the UK in February 2000 and later received top 10 positions globally except for the U.S. where it failed to chart on the Billboard Hot 100. The second single, "Around the World", also peaked at number one in Denmark, but only made number 26 in UK and did not sell highly in most regions. It was the last release in most territories before the band split in 2001.
Scandinavia and other European countries saw further releases of "Bumble Bees" and "We Belong to the Sea" during late 2000, both achieving only moderate success.